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Lysine and Cats: Why It is Not Recommended

Lysine and Cats: Why It is Not Recommended in Cats with Feline Herpes Virus (FHV)I get asked a lot about lysine supplements for upper respiratory infections in cats.  Lysine and cats seem to come up quite often when discussing a sick cat, in a community cat colony or a home!

Many cat caretakers, shelters, sanctuaries, and vets have recommended lysine supplementation in cats who have Feline Herpes Virus (FHV), a type of feline upper respiratory infection.

I do NOT recommend it for the use of controlling FHV. Why? Because it doesn’t actually work and evidence suggests it makes things worse! Read on for my reasoning!

Disclaimer: I am not a veterinarian and this does not constitute veterinarian advice. Please contact your veterinarian for any health concerns you have for your cats. I simply use my experience and research to help educate cat lovers, feral cat caretakers, and rescuers.

Disclaimer:  This post contains affiliate links.  This simply means I will earn a small commission on qualifying sales at no cost to you.  Read Affiliate Disclosure for full details.  Thanks for supporting the kitties!

What is Lysine?

Lysine is an important amino acid that must be obtained through diet as neither your body nor your cat’s body will make its own lysine. It is used the biosynthesis in proteins. It is also important for normal growth and muscle turnover, and to build carnitine, a substance found in most of your cells!

Now, I’m not going to go TOO technical here, but a quick rundown of what it is might be useful for you.

A lack of lysine can also cause some health issues in humans (and cats!) like defective connective tissues, impaired fatty acid metabolism, and more. Too much lysine, caused by ineffective catabolism, and you can have neurological issues.

It’s a biological thing.

For the purpose of supplementing lysine to help with Feline Herpes Virus (as well as human’s herpes simplex virus (HSV)), it is SUPPOSED to work by limiting arginine, another amino acid. HSV (human herpes) is actually richer in arginine and poorer in lysine, and thus lysine supplementation was tried to help control HSV and later, FHV (feline herpes).

Let’s state this plainly:  Lysine is NOT a supplement for immune support.  It is supposed to be a supplement to fight off the feline herpes virus by reducing arginine.

To be clear, human herpes and feline herpes are NOT the same virus. But they are similar to each other.

Now arginine, in humans, is considered a semi-essential amino acid and can be synthesized by your healthy body. No need to supplement it.

However, cats CANNOT synthesize their own arginine. They MUST get this amino acid through their diet. It is considered an essential amino acid for them. It has been suggested that using lysine to reduce arginine (if it works) can be very dangerous for our feline friends.

Cats are HIGHLY sensitive to arginine deficiency! Arginine is very important to detoxify ammonia, which results from the breakdown of proteins. It also has an important function in the urea cycle. According to WikiVet, “feeding a diet that has no arginine but contains substantial levels of other amino acids can result in death within a few hours.”

In kittens, arginine deficiency can cause diarrhea, weight loss, food refusal, urinary issues, and more!

Tiny Orange Tabby Kitten Face

Does Lysine Actually Reduce Arginine?

Lysine does NOT have antiviral properties and will not improve a cat’s immune system, as I stated previously.  Even if it were effective on the feline herpes virus, it would not work on the various caliciviruses or feline chlamydia or other upper respiratory infection agents.

To put it simply, lysine and arginine use the same intracellular transporter system and thus too much of one may affect the metabolism of the other. Notice that I said MAY affect the other. It is a theory.

So far, I have not found any studies that actually state the arginine is reduced in medical studies. The levels of lysine in the blood increase, but that doesn’t mean levels of arginine decrease throughout the body.

Feline Herpes Virus (FHV)Sick Tabby Cat with Feline Herpes Virus

The feline herpes virus is one of two types of viruses that cause most of the upper respiratory infections in cats. It is not as common as calicivirus, but it does account for a large percentage.

Read more about feline upper respiratory infections here.

FHV and other upper respiratory infections cause sneezing, congestion, runny or inflamed eyes, coughing, or other symptoms like fever, pneumonia and in some cases, death.

What separates FHV from calicivirus is that once a cat has contracted FHV, that cat will be infected for life and have occasional reoccurrence of upper respiratory symptoms. Just like human herpes, sometimes the cat shows symptoms, sometimes they don’t, basically. They are also infected for their entire life and occasionally shedding the virus, thus are contagious to other cats.

Calicivirus on the other hand usually gets the cat sick one time, though they may end up infected for months, years, or their entire life.  Sometimes they may even shed the calicivirus and thus be contagious to other cats.

Just like other herpes viruses, the feline herpes virus is high in arginine. Thus, the theory that supplementing with lysine will reduce arginine and subsequently reduce herpes symptoms, how frequently it happens, and virus shedding, which can infect other cats.

Studies on Lysine and Cats

There are numerous studies that have actually proved that lysine supplementation does NOT prevent or help treat feline herpes virus.

Some studies have actually reported an INCREASE frequency of FHV episodes and virus shedding when cats are supplemented with lysine.

In case you’re wondering, it also not effective for preventing cold sores or other herpes symptoms in humans either!

There are many studies published that have proved that lysine supplementation is completely ineffective in FHV cats and/or INCREASED virus shedding and symptoms.

Here are a couple:

BMC Veterinary Research: Systematic Review

PubMed: Study of Effects of Dietary Lysine Supplementation on Infectious Organisms in Cats in a Shelter

PubMed: Effectiveness of Dietary Lysine Supplement in Cats with Enzootic Upper Respiratory Disease

In fact, only ONE study noted that it helped cats with conjunctivitis symptoms from the herpes virus, but that was a seriously small study of EIGHT (8) cats. That’s 4 cats treated with lysine and 4 cats in the control group to compare the two.

There’s a veterinarian article discussing both points of view about lysine, so you can make your own decision.

Though, if you’re still interested in trying lysine supplements for your cats, you can find some on Amazon or Chewy.

Viruses in a Lab

Do I Recommend Lysine Supplementation for FHV? No

Lysine has no antiviral properties. It cannot even be proven it limits arginine. If it DOES limit arginine, that could be dangerous in cats, as they do not produce their own. There have been studies of it proving it actually made symptoms and viral shedding worse!

The only reason lysine was recommended in the first place was based on a HUMAN study on the herpes simplex virus. And just to say, there is no evidence it reduces cold sores either.

I know vets, shelters, and rescues do recommend it. I don’t.

So no, I don’t use lysine supplements nor do I recommend them for people caring for cats with upper respiratory infections.

What Does Help a Cat’s Immune System?

Let’s be clear, lysine was only suggested for use in feline herpes virus NOT immune system response, despite the numerous products that claim it helps a cat’s immune systems.

The most important thing you can do to help a cat’s immune system is diet, to be honest! The better the nutrients a cat ingests, the better the cat’s overall health is, including the immune system.

In my outdoor cat food post, I recommend the best food you can afford for outdoor cats.  This is still true.  Bad food is still better than NO food, definitely.  That being said, the better the food, the healthier the cats!  So my first recommendation is to save the money you spend on lysine supplements and buy your cats better food!

Another suggestion is probiotics!  There has been some early evidence that probiotics help your overall immune system, not just your gut!  It is suggested that it does the exact same thing in cats!

Another suggestion is that arginine supplements actually INCREASE immune system responses in cats!  That’s the same amino acid that lysine is supposed to reduce!  (Though no evidence shows it does reduce arginine in cats). Another possibility is supplementing with salmon oil as the results are promising for that as well.

My last suggestion for boosting a cat’s immune system is reducing stress!  Stress is a key factor in the reoccurrence of the feline herpes virus as well!

Have you used lysine for FHV? Do you think it helped? Or not? Leave me a comment!


58 thoughts on “Lysine and Cats: Why It is Not Recommended”

  1. Hi Rochelle,

    I tried Lysine a few times and it was not as effective as I expected based on all the recommendations to use it. Now I don’t use it anymore. I stick to diluted apple cider vinegar on my cat’s fur since that is actually anti-viral and works wonders. If it is too bad I get antibiotics from my vet.

    I also give my cats an immunity boosting herbal supplement that gets mixed into their wet food. I am always trying to figure out if I should be giving them extra vitamins, probiotics etc. Right now I am trying a mixture of very high quality cat food with all that mixed in with medium grade cat food and some extra supplements. The food has a mushroom extract that is supposed to work wonders for immunity…but it costs a fortune, hence the mixing it together.

    Thanks for this great information on Lysine for cats. I have to say however, Lysine does seem to take down a cold sore right away for me and my husband. I always assumed it is a different virus in cats however and just doesn’t work on them the same way. In any case, it is great to get more information on Lysine in cats.

    1. Hi, Jessica!

      The human herpesvirus and the cat herpes viruses are different viruses, just similar to each other and the way they behave, I believe. Regarding the human herpes virus responding to lysine, all studies on it have been ‘inconclusive’ from my understanding. The studies that suggest it is effective have never been done in a controlled setting, so they can’t prove it was lysine that helped it.

      The one study I wanted to share with you isn’t working on pubmed right now, but the article about it on the Harvard Medical School site is useful too.

      That’s not to say it doesn’t work! They just have no evidence it does except for a couple of studies that weren’t controlled. Other studies indicate it isn’t effective at all. So more work needs to be done!

      But because of those studies that suggested lysine was effective on human herpes simplex virus is how it started getting recommended on the cat herpes virus. Crazy, right?

      Anyway, glad to see another person who does their research on cat supplements! Thanks, Jessica!

  2. I have read other research and posts that support your claim that lysine is ineffective for treating FHV in cats. I haven’t seen any positive reviews for arginine supplements either. My vet isn’t a big proponent of most animal supplements, he syas they just pee them out without any real affect. I think your recommendation of controlling a proper diet is the best course of action to address the issue. 

      1. Rochelle,

        Sorry, but my experience is very much the opposite!!

        I adopted an orange tabby who developed a condition that could not be diagnosed. The condition was one eye was closed!!! My vet could not treat it and in exasperation suggested we could just remove the eye!!!! But he did refer me to a feline specialist in optical problems. HE didn’t know what to do. At this juncture, I spent close to $900 in vet bills. As a last resort, I tried Lysine. It worked, curing the condition within 10 days!!! So I’m sorry. When I think I was tempted to remove this lovable feline’s eye ( who already had his teeth removed when I adopted him), I cringe. So I say thank God for Lysine. You could be giving other cats and cats owners information that could actually hurt our furry pets.

        1. Hi! Thanks for visiting. However, I’m not giving incorrect information. I’ve cited many studies, linking to them, and other veterinary articles that give evidence lysine had no effect or in one study, made symptoms worse. One anecdotal case of it ‘curing’ a mysterious eye problem doesn’t mean lysine helped. It could have been anything as your cat could have been given other medication, could have had a severe eye irritation that cleared up as soon as the foreign body was removed, or any other such thing could have happened. Only in blind test studies where there is a control group (a group given a placebo so that you can compare the results of the study from the group given the lysine versus the ones given a placebo). Nearly all feline illnesses can get better or worse on their own with no interference from people, which is why they have a control group.

          I’m curious, Lysine is only a supplement. It’s only suggested for the feline herpes virus which is an upper respiratory infection. It wouldn’t work on an unknown eye condition even unless it was runny or swollen shut from the feline herpes virus, IF it worked as people claim. And no vet I know would remove an eye unless that eye was damaged irreparably and useless, making an eye removal an improvement for the CAT. No vet I know would remove an eye from an upper respiratory infection unless that eye had completely ruptured. Not even for an unknown cause.

          Now, whatever caused your cat’s eye to close was never diagnosed. It could have actually been something that lysine actually helped, for whatever reason, and not a feline upper respiratory infection at all. IF that’s what caused the condition to get better. If that’s the case, my statements still stand. I don’t recommend lysine for upper respiratory infections. That doesn’t make lysine supplementation worthless. Maybe your cat was lysine deficient. I don’t know. But nothing you said proves it works on feline upper respiratory infections or the feline herpes virus. Just that you think it helped your cat’s mysterious eye problem.

          I’m more concerned with your vet. I suggest you get a new one if they were wanting to remove an eye for an undiagnosed issue for no good reason.

  3. Hi, I just finished reading some very good points here I think it’s probably the same with pharmaceutical companies for humans they are more interested in making money than people’s health.  That’s probably why they recommend Lysine because of the financial element.   I don’t have a cat myself but I do think this is some very good knowledge your sharing here that could help a lot of people.

      1. Hey Lexie: Your spelling is perfect – better than a LOT of grownups. Good for you for getting info on your own!

  4. I’ve heard a little bit about lysine in cats but to be honest nothing so comprehensive as this, so I appreciate your knowledge on the subject. Sometimes it can be difficult to care for cats especially if you have multiple cats. To be honest it seems sometimes that hospitals and vets are more of a business than a place of healing. It’s straightforwardness such as your post here that will not only help people care for their cats, but also keep the hospitals and vets honest. You’ve convinced me that lysine is not a good choice for fighting the cat’s FHV infection, and that a healthy diet is the best option. My cat friends will love your post, thanks!

      1. Sorry to use the reply like this, but could not find where I could comment directly. This study tested all combinations of lactoferrin, lysine, and antibiotics. “The aim of the present study was to verify the efficacy of lysine alone and of the association lysine-lactoferrin against FHV-1 in cats. …These data suggest that the association lysine-lactoferrin could be a first choice in FHV-1 infected cats for reducing clinical signs and viral shedding.” https://www.researchgate.net/publication/287592386_Evaluation_of_lysine_and_lysine-lactoferrin_association_in_cats_infected_by_feline_herpesviras-1?enrichId=rgreq-97a6d05d23c7cf9d42adebebf8205c0d-XXX&enrichSource=Y292ZXJQYWdlOzI4NzU5MjM4NjtBUzozNzUyOTQwNTA0ODgzMjBAMTQ2NjQ4ODQ4MjIxMA%3D%3D&el=1_x_2&_esc=publicationCoverPdf

        1. Unfortunately, that study does NOT have a control group.

          Here’s the problem with the study. Obviously the group treated with Clavamox ALL got better. The OTHER 4 groups were all treated with some lysine type product. There was NOT a control group that was given NOTHING.

          All this study proves is that 100% of the cats in the Clavamox group got better, while lysine was LESS effective. They just ‘phrased’ it as lysine “COULD BE” be an effective first line of treatment for feline herpes and viral shedding. What? They don’t prove anything except that Clavamox works better.

          See, we need a group that wasn’t given ANY treatment to determine the percentage of cats that recover WITHOUT TREATMENT. Do you know how many cats recover from a herpes outbreak without treatment? That’s what you want to determine. You don’t want to prove Clavamox works better. You want to determine if Lysine works better than NO treatment.

          So don’t prove that Clavamox works better. I want you to prove Lysine cats improved in better numbers than the control group of with a placebo or no treatment.

  5. So you’re the Barn Cat Lady. I love ti. Do you live on a farm and how many cats do you have?

    My Mother’s father had a successful dairy farm in the Stoney Rises of western Victoria, Australia. When I was a kid we usually got their once a year. I loved that place there were all kinds of animals including cats. ferrets rabbits chooks dogs cows and snakes. Carrying a length of fencing wire was a must to kill snakes, but I only ever saw a couple.

    I liked the way you explained lysine that was my first question. I knew a vegetarian couple while I was at university. Vegetarianism was almost a religion for them.  From time to time they would mention how their lyfe style didn’t require the killing of animals. I always thought it was ironic that they had a cat which as you indicated needed protein that humans didn’t. So the cat ate meat. Does a cat have to eat meat?

    I like what you said about diet. I agree the immune system requires an extensive range of minerals. And in addition to a good diet, we all need less stress.

    1. Hi! I actually own 3 cats, I have another 3 cats who live in the barn I care for, AND I have 10 foster cats and kittens!!

      You are absolutely right that cats must have meat. They cannot survive on a vegan or vegetarian diet. If they have a cat, they would have to be buying meat. This is partially why I haven’t gone vegan (although health is the main reason!). It seems a bit hypocritical to me if I went vegan to stop supporting the meat industry, then still purchase cat food.

      Thanks for your excellent comment!

      1. Hi –
        I don’t think it’s hypocritical to care for a cat (or multiple cats) and be vegetarian or vegan. Cats are OBLIGATE carnivores–they MUST eat meat. That’s how they’re designed.
        Humans have a CHOICE. That’s how we’re designed. (Sometimes I think we have TOO MANY choices, and that’s actually a design flaw!)
        But a vegetarian or vegan who chooses that diet for health reasons should understand that, for HEALTH REASONS, they have to feed their cat/s meat.
        A vegetarian or vegan who chooses that diet for non-health reasons should understand that, for HEALTH REASONS, they have to feed their cat/s meat. But they can choose WHAT KIND of meat product/s to give their cat. They can choose only organic, or only humanely raised, etc.
        And, of course, another reason we would feed our cat/s meat products–because we love them!

        1. Hi! You’re right that a cat needs meat and there’s no choice about it!

          I believe I said I’d feel hypocritical and here’s my reasoning.

          If you go vegan for health reasons or because you yourself can’t eat animals, then that’s perfectly fine when you own a cat, who has to eat meat in his or her food.

          If you go vegan because you are morally opposed to the meat industry for animal rights reasons or because of environmental reasons, but then adopt a cat, who forces you to buy cat food with meat in it, which in turn supports the very industry you are against. See what I mean? It’s hypocritical. But if you’re aware of the hypocrisy when you go vegan, then that’s cool too!

          I can’t go vegan for health reasons myself, but if I went vegan, it’d be because of the animals and the environment. Then I’d feel hypocritical. Vegan and vegetarian diets often require some supplementation and both diets have been linked to depression, although they aren’t sure if the diet caused the depression or if depressed people are more likely to go plant-based. I simply chose the least cruel options I can, eat as little meat as possible, and supplement what my doctor recommends. But at least I don’t feel badly about having cats who need to eat meat!

          I’ll have to double-check to see if I explained that as well as I did here.

          Thanks for stopping by!

          1. Greetings!
            I’m a vegetarian and I make raw food for my two cats. I grind the meat myself (16 pounds every two weeks, they’re Maine Coons) and include a nutritional completer, heart, liver and salmon oil. I don’t feel conflicted or hypocritical at all because cats are obligate carnivores and will die without meat. For me, I can live healthy without meat. Hope this helps anyone thinking about feeding meat to pets and their humans being vegetarians. 🙂

          2. I just clarified my comment up there. I didn’t mean that all vegans or vegetarians are hypocritical. But the gentleman mentioned they were treating veganism as a religion and how their lifestyle doesn’t depend upon the killing of animals, but they have a cat… THAT is hypocritical. If someone doesn’t want to eat meat or kill animals to consume themselves, but love cats and understand they need meat, awesome. I’m mostly veggie myself, but I have a horrible vitamin deficiency on a regular diet so already have to supplement already and my doctor vetoed vegetarianism or veganism for me completely unless I go veggie with fish (which I don’t like eating fish, so that’s completely not an option). I have no choice. If I went completely veggie, I’d do it so no animal had to die for me to eat, but I’d understand that by choosing to have a cat, I was still supporting the killing of animals for food. Just supporting the killing of them for cat food. But they definitely can’t run around bragging about their lifestyle not hurting any animals if they have an animal they have to feed meat.

            That’s all I meant by that particular comment. It’s for those that are condemning people as immoral for being unable to go vegan, while at the same time, they have to buy meat for their cats.

            Or they try turning their cat vegan, which isn’t good.

          1. I didn’t call vegans hypocrites. I said “I” felt like a hypocrite because I save cats and was forced to support meat production because I love cats, etc. And it’s responses like this is why I don’t like speaking to some vegans.

            I’m vegetarian, BTW. And I actually failed at being vegan due to health issues as I got seriously ill when I tried after about a year. Once I started adding dairy and eggs, I did much better. Not EVERYONE can go vegan, as nice it would be. There are actual genetic differences where some people can properly get nutrients out of an all-plant diet and some people cannot, because these people lack certain enzymes needed to break down certain nutrients into other nutrients. It’s like being lactose intolerant. Some humans can break down lactose easily, despite not being infants. It’s an evolutionary thing humans started developing after they started drinking cow milk. But not ALL humans can tolerate lactose after they’re weaned from mom.

            Some humans can, and some cannot. And my doctor and I learned I did not do well, even WITH a ton of supplements.

            But I did not say vegans were hypocrites. I said that *I* FELT like a hypocrite. Sigh. Many vegans suffer pangs because they feed their cats meat. It is NOT just me.

  6. Perhaps the science does not know why it helps in some cats (note: obviously not ALL cats, based on what virus is causing the URI or your cat’s individual immune system) — evidence anedotally supports that for many cats it does help. Science is always evolving and changing based on new discoveries. Working in a vet office I can say many cats benifit greatly from Lysine, clearing up URI. Two of my cats in fact could not do without it — within a week they will have sever eye issues and will be sneezing out awful snot if they do not have it. Why does it work? No idea. But they need it.

    1. You’re right. Science and evidence is always evolving based on new evidence all the time. The problem arises from doing studies on cats on lysine versus cats on a placebo. Now cats can’t be fooled by the placebo effect, but a lot of the time, URIs will self resolve on their own as they’re viruses and require the cat’s own immune system to fight off. So we can’t know if the anecdotal evidence is actually due to the lysine or due to the cat’s own immune system. Some cats will definitely get better on it, simply because they would have gotten better without it. That’s why anecdotal evidence isn’t actually considered proof. Especially as the studies I’ve seen have all indicated that lysine performs on par with the placebo test, meaning no increase in resolving symptoms. Admittedly, there’s only one study that suggests it made symptoms worse. AND they’re studying lysine on feline herpes, not on every other type of URI there is out there. And scientific studies on cats are lacking in a lot of ways,so it may be we will find out lysine works on in some unseen way on certain things.

      It’s like ringworm and some rescues and vets are suggesting that the treatment isn’t actually working any faster than a cat who isn’t treated since ringworm almost always self-resolves in cats, no treatment required. Which is a good thing with the barn cats, I can’t imagine trying to bathe them in lime sulfur dips or with anti-fungal shampoo. But there seems to be heavy evidence that treatment is not any more effective and it’s simply the cat’s immune system.

      We don’t know. I know just as many people who agree it didn’t work as swear that it did, and the studies I’ve found agree that it isn’t any more effective than placebo, so that’s why I don’t use it.

      It is up to each individual and their vet to decide for themselves to use it or not to use it, of course.

  7. We adopted a kitten that was diagnosed as having FHV or a URI. She would sneeze awful snot rockets, and her left eye would get all gunky. I tried lysine and another immune booster I read about (forget now what it was) and neither seemed to help much.
    However, I went back to the lysine (I forget why now) and have been giving it to her in her nightly wet food snack and it has since cleared up (for about the past year). She’s become a very picky eater and for awhile I was having a hard time getting her to eat it on a daily basis & her eye did indeed get worse when she wasn’t taking it.
    We have a big 22# long-haired cat (Norwegian Forest cat we think) who often has problems with diarrhea (which makes it so hard for him to stay on top of grooming himself – it’s gross). I’ve tried getting him to eat pumpkin, and coconut oil, to help supplement his diet (didn’t work – he wouldn’t eat it). Got the idea to also feed him the lysine if it’s supposed to enhance immune support. So he too has been eating it for the past 6-9 months and has not had ANY diarrhea issues! This has been a godsend!
    I just got online to see if they can eat it daily, or if now that their problems have cleared up, I should maybe be dialing it back a bit to maybe only 4 or 5 days a week… As I know some things you don’t want to take long term.

    1. Ah, but was it the lysine that helped or was it something else? We can never know if something self-resolved on their own, the lysine did something, or if it was a different thing we tried. That’s why I always look at scientific studies. They compare the results of giving lysine to one group and giving a placebo to another group. The placebo group is the control group. Some animals will improve in the placebo group, but if something works, it needs to do better than the placebo group. Lysine doesn’t perform better than the placebo.

      That said, I have no idea if it is a good idea long-term or not. There actually isn’t a lot of research on it in cats, except the two or three studies that indicate it doesn’t work any better than placebo/no treatment. In one study, it even made symptoms worse. But there isn’t a study on long-term effects that I’ve found.

  8. Thank you for this new-to-me angle on lysine. I was about to give it to my kitty but now I’m going to read more and consider carefully. I do feel obliged to comment on two things: I have had absolutely miraculous results using lysine with my own cold sores (I’m a human, btw), and I astonished my dermatologist with the amazing improvement it accomplished in my shingles. Now he recommends it. It’s inexpensive and harmless for humans at normal doses for a short time, so I truly believe it’s worth trying with any human herpes problem. Secondly, I have been vegan for a several years, vegetarian for almost fifty, and I am not at all depressed or unhealthy, nor are any of the many vegans I know. My cardiologist is blown away at my perfect blood pressure at age 70. I wish I could avoid supporting the meat industry in any way, but having rescued many obligate carnivores in my life (and think of them as my closest friends) I don’t feel I have a choice. I don’t feel that this is hypocrisy, just an unfortunate necessity. I would love to see a pet food company produce a food line that is not only organic but as humanely produced as possible instead of factory-farmed. Thanks!

    1. Hi, Sandy,

      I have no idea if lysine would help with Shingles issues or not, that’s one thing I didn’t research. But here’s the problem with anecdotal evidence. It’s not done in a controlled study where one group of people/cats is monitored taking ONLY lysine for herpes symptoms while another group is given a fake lysine. Then they compare the two groups. Because even in the FAKE group, some people WILL get better. But does taking real lysine actually IMPROVE the results more than the fake group?

      In anectotal evidence as when people swear something happens, they tend to associate one thing with getting better. But we don’t know if it was THAT that helped, the body’s immune system, or even something else they took finally started working. We have no idea. And in people, people can be fooled by the placebo effect. Basically, if someone THINKS they are getting real medicine, they actually FEEL better, even if they were given sugar pills. That’s why they test improvement rates against placebo groups. It helps create a baseline on the average number of cats/people who get symptom improvement with NO medicine versus a group given a medicine. Did more people get better then? Or did the same number of people get better? So I put little stock in people’s experience with it. I’m always reminded about people who SWEAR they got the flu after the flu shot. What’s funny is most of the time, they got sick before the flu shot was even given and they experienced symptoms immediately after the shot. But did the flu vaccine actually give them the flu? Not according to all known vaccine studies. Not a single person caught the flu from the flu shot during clinical trials. But some people SWEAR it happens.

      It’s why I look at the percentage of people who improve with a medicine vs. the group that weren’t given the treatment. Because some cats/people will improve with NO treatment at all and we can’t say for sure whether it was lysine or the immune system that actually helped.

      As for the vegan thing, that’s just how I feel. I also have severe deficiencies on some things even ON a normal diet and have to carefully supplement as it is. My doctor warned me not to go vegan. Some people absolutely CAN and do thrive that way. I just can’t. I do however try using more humane options than factory farming. Free-range chicken eggs and I’ve limited my meat. And many cat food companies will do the same, but it can get pricey. And when you care for dozens of cats, they might not be able to afford ethical cat food. So it’s a toss-up. *I* just feel a little hypocritical that I feed my cats meat by necessity and can’t afford more humane options for them without going completely broke and that I myself can’t thrive on a vegan diet. But anyone that tries reducing the cruelty of their food intake is helping, too, whether by going vegan or even just free-range. The meat industry IS changing thanks to all of that.

  9. Harry Koudounas

    I didn’t know about L-Lysine, until my veterinarian told me, to try, as an adding factor for a serious case I had with a cat of mine.

    But look, that was as a plus only. She said, well you can also try to give some L-Lysine, it may help.

    The cat was found in the neighborhood near to death, dehydrated, with serious weight loss, and serious rhino sinusitis, actually nose and lung infection. Nose liquids, not eating etc.

    That was not FHV. The vet told me as a sinus virus with companion bacteria. We made antibiotic injections (I think 3 times every 2 days), Vet told me that they were Amoxycillin, she also told me to continue with Amoxycillin by mouth (Augmentin), or alternatively with Doxycycline (Vibramycin).

    We continued, the cat started to eat, and get weight every day. But the sinusitis was continuing also.

    We even got lung X-rays, and the X-Ray lab told me that sinusitis may go a chronical problem for life.

    May the inner of the nose, had some distruction by the long time infection.

    I lost my faith, using Augmentin (1 week) or Vibramycin (1 week), for a long time (15 days), until the Vet told me again to insist with Amoxycilline for up to 25 days.

    You may also use some L-Lysine in the food to help, she said.

    We went for the antibiotic cycle for 25 days using an other antibiotic, Amoxil, calculating the doses per kilograms of body weight, and the 12 hour cycle of the doses, with integrity.

    So, the miracle happened, and that so difficult sinusitis vanished!

    To say the truth, I also help the cat with good nutrition and vitamins. So, I can not conclude if the L-Lysine helped or not. But I’m sure my success was the long time (25 days) of the antibiotic cycle, and that for me and my cat, Amoxicillin finally worked.

    Today, it’s sinusitis is gone, but it left some little remain, I hear it, when he sleeps and snores.

    I had many FHV cases with other cats. The key factor is time. Time is critical, to save the eyes, and start antibiotics immediately, also antibiotic eye drops / antibiotic eye cream, we use Tobrex (Tobramycine) as an eye drop antibiotic.

    Or if you have a serious case, you go to the vet for antibiotic injections as the start of the therapy, and you continue antibiotics by mouth, and eye drops.

    The tragedy is always, if you lost time, and you lost an eye, or the worst, both of the eyes. But in some cases, the cat can be saved with a medium eye damage, but she will have vision after all.

    My conclusion is: L-Lysine may add some help (?) but the basic is the antibiotics, both for the body, and for the eyes (drops).

    And of course, enforcing the cat with nutrition, vitamins, fish oil etc.

    1. Absolutely! L-lysine is often used instead of medication. Of course, as long as proper meds are used as well, it’s not harmful and ‘may’ help. Just at this time, there’s no evidence it helps the feline herpesvirus, but that doesn’t mean it isn’t beneficial or effective for other issues, just they haven’t studied it.

  10. I have a cat that came from the shelter with some sort of URI, his eye got gunky and he sneezed bad. The vet said it was FHV by never ran tests so take that with a grain of salt. They sent me home with a l-lysine paste to give him and he did get better. I agree he might have gotten better on his own. However, fast forward in time and he had flare ups. I didn’t believe the l-lysine helped, but I finally felt bad for the guy. He be miserable for a few weeks every time he has a flare so I bought some. Wow! He cleared up in one to two days of his first dose of the stuff, and if I stopped giving it to him too far the flare up comes back. I have no idea why it works or if he even has FHV for real, but it does work for him, and I used it on a pair of feral born kittens in my yard and they cleared up too. Take the info or leave it, but I’m going to use it because I can’t stand listening to my poor guy sneeze, shake his head, and mope around miserable. The vet also recommended having him get shots for FHV regularly but he is so traumatized by going to the vet and the l-lysine world better than more shots ever did.

    1. Hi, Dawn,

      Some people swear by L-Lysine. It did nothing to help mine. So I decided to research studies on it. That’s when I realized ALL the studies they’ve done show it performs no better than the control group who is on a placebo! In humans or cats! That’s when I made my decision.

      But here’s my other problem with L-Lysine supplements. It was recommended for FHV only, right? (And yes, your vet diagnosing without doing lab tests to determine if he or she is right isn’t very cool. MY vet doesn’t recommend those tests all the time either, but he calls all of those types of illnesses, upper respiratory infections or URIs. He doesn’t suggest WHICH type of URI it is without doing lab work. He usually just treats the secondary infection with antibiotics and waits for the cat’s immune system to fight off the virus. If that doesn’t work, THEN he suggests those tests.) But then these people decided to make MONEY off of L-Lysine and started marketing it for IMMUNE support, instead of marketing for what doctors were hypothesizing it would do for the herpesviruses. The ONLY studies I’ve seen that support L-Lysine usage is for those people who are lysine deficient! Everything else is a “eh, maybe?”

      Here’s my other problem: supplements are not regulated by the FDA or any agency until AFTER a complaint has been made and the FDA tests the product to be sure the product doesn’t contain actual drugs, prescription or otherwise, or other ‘hidden’ ingredients not included on the label. So who’s to say the supplement company didn’t add something extra to that lysine, like antibiotics or antiviral medications, to help it fight off severe URI symptoms. We don’t know. By law, they’re not supposed to. But there are hundreds of supplements that have been pulled off the shelves by the FDA after it was found to contain prescription drugs, illegal drugs, or other problematic ingredients without proper labeling. You think I’m kidding, but I’m really not. Male enhancement and weight loss products are the two most common ‘supplements’ that companies will include prescription drugs in them to make them actually work JUST to make money. I do a LOT of research on supplement companies before I choose one for myself, let alone my pet.

      But yeah, it may have worked for you and maybe it was legitimately lysine, and maybe it was the cat’s immune system as well as any other meds the vet prescribed. Anecdotal evidence gives us hints onto things to study, but it’s not accepted as proof scientifically. By all means, keep using it if it’s working. Maybe your cat is just lysine deficient and that’s why it helps! In which case, great.

      But it didn’t work for me and all studies I could find testing lysine on FHV indicate it doesn’t perform any better than a placebo. Add in my irritation on their marketing practices and lack of trust in companies who deal in supplements, I still don’t recommend it. ^_^

  11. My 18 year old cat was sneezing heavily for a whole year. It was on the walls, the furniture, ouch … I tried everything from herbs (ginger, thyme, spirulina, echinacea, vitamin c …) to massage and (even more) stressfree living. He was always fed grainfree wet food, never any dry food, and still is. So his food has always been pretty good. About a year ago I tried l-lysine with vitamin B6 (excellent combination) and the sneezing stopped within 2 weeks! The sneezing never returned. He since gets a tiny maintenance dose daily. As I write this I have a happily content non sneezing cat purring on my lap. Since a few weeks I give him some good quality probitics. He’s on his way to 19 and still jumping high … literally and figuratively. Just wanted to share my experience.

  12. I just discovered this by accident in looking for the video made by alley cat allies about relocating, I know know know its a last resort, but we have a rural animal control in next county who sometimes gives free roaming cats to barn homes. He and I were talking about it and I told him I would send him that video. He is not going to stop supplying the barn owner with cats. so at least the barn owner may watch the video , and if he cares enough , give those kitties a better chance. thank you for the info in your newsletter

    1. Hi, June,

      Sorry for my late response, I was on hiatus.

      *Sigh*. I wish animal control would think about the cat for a minute before doing that. It’s not the first time I’ve seen that. They really need to do that with cats that CANNOT be returned, not ALL cats. But yeah, rural areas are very behind the times sometimes and they’re tired of euthanizing for space, I guess it’s better than them being killed, maybe?

      I mean, hopefully, they’re fixed and the cats are contained in a crate or tack room before being released. But thank you for looking for information to help pass on to them to make it better for the cats!

      Hopefully my information helped!

  13. In my experience, Lysine ABSOLUTELY works well to treat Herpes in cats. I work with animal rescue, and have use Lysine MANY times to treat Herpes in cats – very effectively.
    Based on the experiments I’ve seen on Lysine for Herpes – THE LYSINE IS NOT USED CORRECTLY.
    Lysine must be given in AT LEAST 2 separate doses each day. Otherwise – you can easily get a rebound effect if you have a high germload.
    Lysine is effective against many germs (Including Herpes). If you dose the Lysine only ONCE a day – you inhibit the reproduction of lots of germs all at one time – and – then – if you wait too long, the germs seem to react as if the Lysine has been STOPPED. So – all the germs seem to START reproducing again – at the same time. (This is my own theory – BUT – since I have often used Lysine for myself – and I have a high germload – I can verify that the rebound happens if the time between Lysine doses is too long.)

    1. Hi, Jackie,

      I don’t know the dosing schedule for each study they did. I just know there are TONS of studies done on lysine and herpes, both humans and cats, and I looked at the results on that and I am not a doctor so I cannot tell you what the ideal dose is for lysine for humans or cats. But even vets or doctors can’t tell you because supplements aren’t studied to the extent that medications are studied before they are released to the public.

      With medication, you have a dose that they KNOW is effective for people based on their weight/size, and they KNOW the dosage of when it becomes toxic, and they KNOW most of the known side effects. For supplements, they just… guess, because supplements have a very wide margin of safety before they become toxic. But there are very few studies on how our body absorbs any supplement. Because you can’t take lysine or vitamin D and then do a blood test to tell if the supplement is still in your system because we get Lysine and vitamin D from our foods naturally too.

      And do you know what happens if you have too much lysine or vitamin C? Your body just passes most of them out in the urine, except fat-soluble ones, but you can cause toxicity if you take too much for too long of a period of time. Too much extra lysine causes gallstones and renal failure. Too much vitamin D causes calcium to build up in your blood, which causes illness and can cause kidney stones and kidney issues. It doesn’t make your body function better or cause your body to work better, it either gets completely wasted by being urinated out or it starts building up in your body since your body isn’t using it up.

      To be honest, supplements are not well studied at all. They can be very useful if you’re say, iron deficiency or have pica due to iron deficiency, iron supplements are great! Or if you are pregnant, then folic acid supplements are vital. Or if you have a vitamin D deficiency then you definitely need a vitamin D supplement. So supplements absolutely have their place in medicine!

      But as they have no actual evidence that adding a lysine supplement helps with feline or human herpes viruses, especially as humans and cats get lysine from their food, too.

      But there IS evidence that Clavamox and anti-viral medications help improve herpes symptoms in cats and there are many medications for humans for herpes flare-ups too. So why would I waste money on a ‘maybe it works, but there’s no evidence yet’ instead of one that has PROOF it helps?

      I rescue cats in my spare time. I look into ways to save money on vet bills and stuff because I’m definitely not made of money. I didn’t want to waste money on something that may not work, because that could be expensive and I’d still have to see a vet for the correct medication. Plus, the added stress of giving supplements, as my cats are picky about food additives, I do not think it’s worth it. Especially with limited funds, you don’t want to waste anything.

      And vets are now stopping the lysine recommendation with all the research that has been done at this point.

  14. We adopted a stray cat from a strip mall my daughter was working at. He was frequently seen in the garbage bin behind the Chinese restaurant, and she and employees would feed him cat food. Winter was coming and she asked if she could bring him home. He stayed in the dog crate in the garage, and we took him to the vet asap. He got his shots, they plucked the ticks off, applied flea meds, etc. Vet noticed his eyes and nose was runny, and told us to buy lysine and crush tablets into powder and sprinkle on food. He was 9 lbs. His runny eyes and nose cleared up and needed no further treatment, and that was exactly ten years ago. There is an article that explains how this works. Viruses need arginine to replicate. Arginine and Lysine have similar properties and viruses latch on to Lysine if it is present in sufficient quantity, and this lowers virus replication so the immune system is not so overwhelmed that it cannot work properly. Meanwhile the arginine is used by the cat as it is a necessary nutrient. There is a scientific report that explains this a at Whole foods magazine, or just Google “Lysine halts coronaviruses”.

    1. If you had read the article, I explained how it is THEORIZED to work, because by flooding the system with lysine, the arginine rich virus wouldn’t replicate, they THOUGHT. And it’s only supposed to be effective against the feline herpes virus, in THEORY.

      Which is NOT a coronavirus, btw. Feline coronavirus causes diarrhea and rarely FIP, nothing to do with any feline upper respiratory infections. Whole Food Magazine isn’t a scientific journal studying medicine, either. They are very biased on what they claim with no evidence. Whether or not lysine helps with coronaviruses has not been sufficiently studied or proven.

      In ALL lysine clinical studies on actual cats with feline herpesvirus, it doesn’t work. One study actually found it made symptoms worse.

      One cat improving while taking lysine proves nothing. Most upper respiratory infections in cats are caused by different viruses, not necessarily just feline herpes. You don’t even know which feline virus caused the illness. AND cats usually get better on their own from upper respiratory infections, just like humans recover from colds on their own.

      You cannot know for sure whether the cat’s own immune system did it’s job, it was something else you gave her, or it was the lysine.

      Since the cats in lysine studies were separated into two study groups: one group got fed lysine, one group got fed a placebo or fake lysine. BOTH groups had some cats get better. BUT the lysine group did not have MORE cats improving than the placebo group. They had the SAME percentage of cats improving! That’s how you tell if something is not effective. If more cats aren’t getting better than fake stuff, obviously it doesn’t work.

      Let’s put it this way. No medicine is 100% effective in all individuals. In order to determine, say, benadryl relieves allergy symptoms, they get a bunch of people with allergies together that aren’t allowed to take anything but what the study gives them. They then split the people into 2 groups. 1 group gets benadryl. The other group gets a placebo or fake benadryl, but they are NOT told its fake! Then they see how many people’s symptoms are reduced in each group. If more people are not suffering from allergies in the benadryl group than the fake group, then it works! If the 2 groups have the same number of allergy relief, benadryl is NOT effective. Because benadryl doesn’t work on everyone, there needs to be MULTIPLE people getting it and because people get better on their own, there needs to be a fake group to make sure there’s a baseline of improving with no treatment.

      Same thing was done with Lysine. It did not improve more cats than the fake lysine group did. Thus, doesn’t work.

  15. I had a 6 months old kitten that couldn’t get rid of conjunctivitis due to FHV. I gave her L-lysine in her food for several weeks – can’t remember dosage. She developed acute kidney failure and she died. When I read about a study with rats and L-lysine, it causing kidney failure, I’m afraid I’ve caused her death. I’m not keen on any supplement anymore, just invest in very healthy food and try give them a stressfree home.

    1. Hi, Ingrid,

      I am so sorry for your loss! I believe you mean this study of lysine and other amino acids. You’re absolutely right that high doses of lysine have caused renal failure all by itself in rats. Considering cats are often prone to kidney problems as it is, this IS something to consider! There is no concrete evidence that lysine causes kidney problems, but there IS evidence that cats with existing kidney problems don’t get lysine out of their systems well. Lysine can also cause allergic reactions.

      Another thing to consider is that supplements are NOT regulated carefully like medications are! To be honest, we have NO idea what is in most supplements on the shelf! Supplements have often been pulled off the shelves AFTER it’s been found to include well-known prescription drugs like diet medications and erectile dysfunction medication, things like that. So if you don’t trust the company, you shouldn’t try that supplement. For all we know, these lysine supplements people are feeding have antibiotics in them, being given in inappropriate amounts and THAT is why it works on their cat. We have no clue. Once I learned how anyone can market a product as a ‘supplement’ and it is only regulated AFTER the FDA decides to test the product on the shelf, who knows how many years after it started being sold, I’ve been very, very leery of supplements myself. At least with medications, you KNOW it’s regulated, that is what you’re getting, and you know it’ll probably work. And if you have a bad reaction, you can say, “I won’t take that medication again” and just avoid it. But supplements can contain ANYTHING. They absolutely can be pulled off the shelf by the FDA. But by then, it may be too late for some people. Or cats.

      I’m sincerely sorry for your loss. I don’t know if it was the lysine, something within the lysine, or the kitten had a congenital kidney issue (the Kitten Lady has one with kidney problems since birthright now) or what, and we can’t prove it with science right now, but you brought up a very good point that lysine HAS been proven to cause kidney issues in rats at high doses.

      Everyone likes to assume ‘supplements’ are safer than drugs. They aren’t. I’d love it if lysine worked for URI symptoms of feline herpes. I really would save SO much on vet bills. But the idea of it already made me leery when there is no proof it works. The idea that it may also cause kidney failure? Super scary!

      Thank you for sharing your story!

  16. Dr Joseph Carlson

    Lysine absolutely is anti-viral… that’s why it works great for people with shingles (Herpes Zoster), cold sores, the flu, etc, etc especially if taken at the first indication of any flareup (and especially as a prophylactic)… it’s also why it’s often the only active ingredient in the medicine vets prescribe for URIs in cats (the rest is just fillers and flavorings). The science isn’t going to change on that any sooner than the science of water being wet is going to change; lysine always was and always will be anti-viral, it’s just which viruses it has an effect great enough with to notice a difference, and with cats you almost always notice a huge difference in just a couple days. Lysine has proven to help with literally millions of cats for many decades and most of those occurrences certainly would not have cleared up within a couple days like they often do with lysine.
    You should stop giving advice on things you clearly know very little about because wrong information is often worse than no information.
    I’m assuming you’ll either delete this or not display it in the first place (whatever, it’s your sandbox (or litterbox – lol) so it’s your rules), but at least spend 5 minutes to find out for yourself whether or not you were wrong (you were) and if you’re relaying wrong information (you were).

    1. Give me ONE study where lysine performed better than no treatment. Just one. It can be human, cat, or guinea pig for all I care. It is studied almost exclusively with herpes viruses in cats and humans, but if you can give me a study where lysine was used to treat ALL SORTS of viruses and WORKED against ‘no treatment’ control group, I am ALL ears.

      See, you can’t disagree with my assessment of scientific studies without actually GIVING me a scientific study to contradict what I’m saying.

      I don’t honestly care if lysine works or not, that’s what you all don’t seem to understand. I would LOVE for it to work, less money on vet bills, just give them lysine! But I canNOT find one SINGLE STUDY where lysine worked better than a placebo/control group. So if you want to change my opinion, that’s how you do it.

      Opinions don’t matter to me. It’s unbiased studies that I’m looking at.

  17. As with most studies, researching your bias, what you want the result to say; will be just as anecdotal as the evidence against your theory.
    And no, pharmaceutical companies are not trying to push natural remedies to anyone; they’d rather you pay top dollar for antivirals.
    Humans have had a lot of success using L-lysine for HSV.
    This is an opinion piece, backed by cherry-picked research and could send humans down the wrong path, not only for their kitty, but for themselves.
    I noticed, if people agree, oxytocin boost! “Thank you!!!!” Rainbows and kittens, if someone disagrees, you’re not thrilled about it, don’t research further, research against your bias, and type paragraphs about how you’re right.
    I won’t be coming back; I just hope with others’ and my own comment, people will ask their vet and/or doctor and do their own unbiased research. Thank you. Take care.

    1. Hi, Boognish,

      If you can link ONE study where there is ACTUAL evidence of human OR feline herpes actually getting BETTER with L-Lysine, then you are more than free to give me that link. You’re disagreeing WITHOUT proof. Give me the proof it works, without saying, “I tried it and it worked for me!” I mean actual scientific studies where there was a noticeable improvement in herpes symptoms with l-lysine. Just give me ONE published study! Just one, from cats OR humans!

      See, I don’t actually care if l-lysine works or not. I had NO opinion on it when it was first suggested to me. I just did my research to determine if I wanted to try it or not. That’s all. I didn’t decide NOT to try it and THEN find studies, like you are suggesting.

      I’m not even against natural cures! AS LONG AS THEY WORK! Many of today’s medicine comes from nature! Aspirin, narcotic pain medication, some antiviral medications, etc, etc, etc. All of those substances we call medicine was usually first ‘discovered’ in nature. But science decided to make willow bark into a more concentrated form and now we have aspirin! Way more effective than brewing willow bark tea and much stronger than the tea. But the EXACT SAME INGREDIENT!

      So no, this isn’t an opinion. I am just against pushing a product that doesn’t work. If it actually worked, I’d suggest it to people, as I do with diatomaceous earth in carpets for flea infestations. But since l-lysine doesn’t work, I don’t.

      I looked at ALL studies that I could find, that isn’t cherry-picking anything. I didn’t ignore the evidence I didn’t like. I DID NOT FIND EVIDENCE! I found evidence of it not working better than a placebo.

      I literally GAVE you scientific evidence of studies and YOU are choosing to ignore that evidence in favor of YOUR opinion. THAT is exactly what cherry-picking evidence is. Not me.

      And everyone should talk to their veterinarians about their cat’s health prior to doing anything. But just like human medicine, some veterinarians have looked at the studies and agree it doesn’t work any better than a placebo and some vets haven’t seen the studies yet.

      And there IS one study that suggests l-lysine actually made the symptoms worse in cats, so I wouldn’t say it was ‘harmless’ to try either.

      But seriously, if you disagree, that’s fine, but you gotta give me proof before you insult people for stating facts that YOU don’t believe. And by proof, I mean unbiased peer-reviewed scientific studies. Just find ONE and I’ll take the article down until veterinarians can decide if it works or not.

  18. I don’t know what pathogen my cats have had . Watery eyes – sneezing … lapping at the mouth …. kinda like a common cold for humans .
    The lysine works . I’ve don it simple cause and effect . Don’t know the studies out there they could be legit .
    BUT I know this . We get lied to all the time . Why / MONEY !! We have been lied to about the CV 19 from day one …. I could list much of it . BUT . Either one accepts though critical thinking or not that the medial community lies for money or is ignorant for ego .

    Give me ONE study where lysine performed better than no treatment. Just one. It can be human, cat, or guinea pig for all I care.
    OK you want a study … here’s your damn study … NIH
    We recommend the inclusion of lysine supplementation in addition to a reduced arginine intake for the prevention and treatment of SARS-CoV-2 and IAV infections.

    1. Hi, Duncun,

      That is not quite what I meant. That is a study of CELLS and VIRUSES in a LAB with COVID-19. I’m not saying Lysine is worthless, it IS an important amino acid after all. But even in a lab experiment, they do NOT know if ingesting lysine will reduce COVID infections. They also noticed that reaction to the HERPES virus in the lab, but when they give lysine to people with herpes, there was NO effect on flare-up symptoms! That’s why they started recommending it to cats, BECAUSE OF LAB experiments.

      Science doesn’t lie. Our UNDERSTANDING of it changes as we learn more. Scientists are NOT in it for the money, I guarantee you that! But lysine is a SUPPLEMENT that’s marketed as a cure-all for everything JUST to make money. Why would you trust a BUSINESS over scientists? Businesses make WAAAAAY more money than scientists EVER do. And the lysine is a MONEY maker ALL because of ONE lab experiment.

      They don’t know why lysine itself directly prevents viral infection in lab experiments but when studied on ACTUAL patients it completely fails. THAT is the studies I’m talking about, the studies where they took an animal (like a cat) or a human and tested HERPES viruses and lysine in one group AND test “No Treatment” or a Placebo in another group in the SAME study.

      It’s actually easy to see which ones are legit! I can’t read a lot of the really technical studies as most people can’t, but I CAN read studies on LIVE test subjects and EXACTLY what to look for: Studies of one substance being tested against NO substance. Any study that does not test live subjects against a placebo or no treatment is not performing a study on effectiveness, so they can CLAIM whatever they want, like it “MAY” be effective. That language is suspect. MAY means they can’t claim that it IS effective.

      The body, ours and cats, are amazing machines. Our livers and kidneys filter out toxins, our digestive tract helps extract the nutrients our body needs, but NO one knows how taking a substance will work once INSIDE a body unless they TEST it on a body.

      There IS one study where they give one group Clavamox, then THREE groups Lysine in different dosages and guess what? Clavamox cured 100% of the symptoms and the three lysine groups were a lot less effective. So not certain what THAT proved (except that Clavamox works WAY better) since they didn’t have a control group or a ‘no treatment’ group in that study. But they tried to SPIN the results of that study to say “Lysine may be effective in treating herpes virus” even though CLAVAMOX was MORE effective, but they NEVER tested it against “no treatment”. It was also a study RUN by a company that sells lysine, so VERY suspect!

      To determine if something is effective, they test it in a lab. If it shows promise, they then test it on animals and then people.

      Lab experiments don’t prove effectiveness, only LIVE subjects do.

      Bleach kills viruses in the lab, right? But no one is about to go around drinking bleach to prevent infection. Sunlight kills viruses like COVID-19 in the lab too, but yet you can still be infected during daylight hours if someone sneezes on you. Lab experiments aren’t proof. They’re an INDICATION of an avenue to study.

      So find a study with human or feline test subjects where lysine is given to one group and “no treatment” or placebo is given to the 2nd group and with the LYSINE group actually performing BETTER than the “no treatment’ group. THAT is what we’re looking for.

      Scientists aren’t lying to you about COVID or anything else. But supplement companies ARE lying because weight-loss and male enhancement and other supplements are a MULTI-BILLION DOLLAR enterprise! They make BILLIONS upon BILLIONS of money because supplements are NOT regulated by the government and people want EASY fixes without having to work to lose weight or go to the vet for the pet, etc. And people TRUST what is on the bottle even though it could CONTAIN ANYTHING!

      Did you know the FDA has an ENTIRE LIST of recalled supplements that they randomly tested and were found to contain DRUGS?! Prescription AND illegal drugs! THAT is why I research before I give my pets or MYSELF any supplement.

      Don’t get me wrong, supplements have their uses. I use vitamin d, calcium, and magnesium because I’m deficient in all of those and actually need them. But I research ANY others that people recommend to see if something WORKS. And some supplements DO work, absolutely! CBD actually seems to be effective, as are things like Kratom or marijuana and other ‘plants’, but most is just a waste of money and IF effective, they are less effective than medicine actually is because science have already found out what substance in a plant makes it work and reproduced it to create medicine. And supplements are no safer for people than medicine is. IN fact, can TOTALLY be MORE dangerous because supplements have to pass NO safety studies before they can be sold!

      I did research this before I decided against Lysine. I honestly hoped it WOULD work, then I could save on vet bills. But I will NOT put my cats at risk by giving them something that is at best, ineffective, and may end up making things worse.

    1. Hi, Mark,

      Actually, I’ve been very respectful in my disagreement with all the comments I get where people give me their story on a cat they feel lysine helped.

      You guys don’t get it. I’m not biased. I’d LOVE for lysine to be effective. Do you know how much MONEY I’d save on vet bills rescuing all these cats dumped on our property? I’d LOVE for it to work! I WANT it to work.

      But I also understand science and I don’t use ANY supplement without science backing it up and lysine has literally ZERO studies backing it up as being more effective than NO treatment. I’ve asked people with their disagreements to give me ONE study where it worked. Just one. That’s all I’m asking for. I’ve also VERY kindly explained why their cat getting better on lysine doesn’t mean it actually works AND I’ve explained how studies on lysine are performed.

      Seriously, if one person can prove me wrong, I’m all ears. Do you know shelter medicine vets are no longer recommending lysine now because of all the studies that have demonstrated it’s completely ineffective?

      Herpes is a virus that causes occasional symptom flare-ups. That means it GETS BETTER ON ITS OWN often. So by giving lysine, how is ANY regular pet owner to know that the lysine is what helped, or was it the cat’s immune system that worked? We don’t know! That’s why they actually study it!

      But seriously, give me one study where lysine performed better than a placebo or no treatment. Prove me wrong.

      But don’t suggest I wasn’t PERFECTLY polite while discussing this.

  19. Interesting article. my 10-year-old cat, Sid, has herpes. He eats like a horse and sometimes sneezes like one. Every once in a while, I give him an antibiotic but have never used Lysine on him although the vet I work with recommends it. I am trying the Lysine gel although he hates it. For me, Lysine is a miracle worker. I have high acid content and would get multiple mouth ulcers. I even had to go to the doctor once and get some kind of a liquid mixture to put on my mouth because the pain was so bad. I began taking three small lysine tablets every day and now I seldom get an ulcer. Sometimes, if my nerves act up or I get a lot of stomach acidity, I can feel one starting up. But it quickly fades away. So, I think I will finish the lysine for my cat. Maybe try a different kind though. He also probably has allergies as well because warmer weather seems to make his eyes water more. Don’t know what I can do for that.

    1. Hi, Anita,

      I can’t comment on whether lysine helps because of acidity and mouth ulcers, I’m definitely not a doctor or vet. Lysine IS a very important essential amino acid that ALL our bodies need to function and humans NOR cats can produce our own lysine, so we get it from our food. It has a very important function. And if a cat’s diet or our own diet is lacking in lysine, supplementing with lysine is a good idea. And it won’t cause harm if given to the cats or ourselves.

      However, supplements that we don’t need, just get flushed out of our bodies. I’ve had this discussion with a doctor once. Amino acids, vitamins, and minerals are vital, important building blocks for our bodies to run properly. However, if we give our bodies MORE building blocks than the body can use, the body just gets rid of everything extra or it can reach toxic levels as people have literally poisoned themselves by taking too much Vitamin A. Honestly, excess levels of ANYTHING can be toxic. Just look up water toxicity, which dogs can actually die of.

      So it’s important to use supplements when they actually work or when they are actually needed, otherwise you’re wasting your money as you’re basically urinating it out of your body OR you are possibly overdosing, which can lead to things like kidney stones with some supplements.

      So sure, try it on your cat if you want. It’s probably safe enough. But there’s not evidence yet that it every worked.

  20. I have saved the lives, not to mention the eyes of at least four kittens w/Lysine. Severe cases of FHV. You most definitely
    are causing harm if someone reads your site and decides against lysine cos without lysine that cat or kitten may not
    make it. You are never going to find any studies where they say that Lysine was effective, period. You will never
    see a study like that because there is no one that would make a profit from Lysine. So there is no reason
    anyone would invest the money to do any kind of clincal or double blind or any kind of peer reviewed
    study. They do those when there is a drug they want to profit from . If you do not put a small amount
    of vit C with the Lysine it is not going to work as well. You don’t want to OD your cat either. I see things
    recommending crazy amounts , saying it is “safe”. Error on the side of caution. It is better to give them too
    little than too much. You can add more, but you can’t take it back. The smaller the cat the less you need.
    I have seen kittens with eyes that were so messed up you would think nothing can be done. Just really
    sad and terrible sights. Lysine can save those eyes. It also stops shedding of the virus so that it isn’t
    just sitting around for other cats or kittens to catch. Don’t give too much vit c or they get the runs.
    I would say for a kitten 25mg lysine vitC 5-10m at the same time. Every 4 hours and you should
    see an improvement certainly by the third dose likely with the lst. Full grown cat about 50 mg lysine 20
    vit c. Once you are sure they are out of the woods you should stop giving it to them. It depletes arginine
    so it is not something that is good for a daily thing. Hope someone see’s this in time to save their kitten
    or cat. P.S. NO I am not a vet. If I were a vet I wouldn’t be leaving this message for the same reason you
    won’t find many studies. Thank You

    1. Uh… do you not understand how businesses work? Or scientific research studies for that matter? What you’re saying doesn’t make sense.

      You do realize supplement companies make BILLIONS upon BILLIONS of dollars just selling supplements to people and they don’t even have to WORK! O.o The global dietary supplements market size was valued at $151.9 billion in 2021.

      If lysine worked, I could promote lysine to MAKE MONEY to help MY colony of cats and my fosters. Why would I lie about this? I could make LOTS of money off this one page alone! Just like supplement companies make BILLIONS of dollars off these products.

      But I care about the CATS and the people caring for the feral cats and I try to help them take care of them with EFFECTIVE solutions, not just make money. Most people caring for ferals cannot afford a vet. I’d be the FIRST person to promote lysine if it worked.

      That’s the difference between being skeptical and being in DENIAL. Skeptical people ask for proof. People in denial won’t BELIEVE the proof. I am not in denial. I have an open mind. I’d LOVE for it to work, I’d make SO much money if it did. But I want to help cats and people more.

      There’s no evidence lysine works for feline herpes virus or boosts a cat’s immune system. (Not something I recommend anyway unless a cat has an immune DEFICIENCY like FIV. Boosted immune systems leads to autoimmune disorders like allergies and Systemic Lupus Erythematosus in cats.) Lysine may work for something else, like people/cats deficient in lysine, but it absolutely has no evidence it works – as of now – for herpes, feline or human.

      IF there WERE a study suggesting Lysine worked? The pharmaceutical companies would JUMP on lysine like butter on popcorn.

      “By definition, Alternative Medicine has either not been proved to work, or been proved not to work. Do you know what they call Alternative Medicine that’s been proved to work? Medicine.”

      “Alternative medicine is any practice that aims to achieve the healing effects of medicine, but which lacks biological plausibility and is untested, untestable or proven ineffective.” – Definition of Alternative Medicine.

      When something is shown to be effective, it is turned into medication or used in medicine.

      Supplements are sold EVERYWHERE and the whole supplement market is a multi-BILLION dollar industry. They make billions of dollars selling supplements and BONUS, they do NOT have to prove they’re SAFE or that they WORK before they can make money. BILLIONS of BILLIONS of dollars here. And you think Big Pharma and the medical field are the enemy? Supplements is a business all its own, you know.

      While some supplements can be used to treat some conditions and some supplement companies are ethical, there are MANY that are complete and utter scams, basically. AND THERE IS NO WAY TO KNOW which ones work, which companies are ethical, and which ones are SCAMS, with actual medications in them. That’s not even counting the majority of them that don’t work at all.

      They Big Pharma & Supplement Companies make BIG money, but BIG PHARMA is REGULATED by the FDA and other agencies AND has to prove it WORKS first and is SAFE for most people. Supplements are completely UNREGULATED until AFTER they’ve been sold and cause harm and they STILL don’t have to WORK to be sold.

      Why would ANYONE with a logical mind take to using UNPROVEN supplements (a business) over effective medicine (also a business) then?

      Since BOTH Big Pharma AND Supplements are in JUST to make money, I looked into scientific research to make my decisions.

      But anything that is PROVEN effective in studies is NOT suppressed. They just turn it into MEDICINE.

      Willow bark tea is a ‘natural’ remedy that once people used for headaches. It was proven to work. Do you know what happened? Aspirin was invented because willow bark tea contains aspirin. ALl they did is take out all the INACTIVE ingredients and made it into EFFECTIVE, MEASURABLE doses. Nearly ALL medicine started in ‘natural’ or traditional remedies.

      I even take supplements myself! But I’m also an intelligent, reasoned human being that relies on proof of effectiveness before I start just taking supplements.

      Supplements are NOT regulated by the FDA or ANY other government agency until AFTER they receive complaints. For all you know, all these lysine supplements being sold online contain ILLEGAL antibiotics and THAT is what is making L-Lysine supplements effective. Don’t believe me? Go to the FDA website and look up their supplement and drug recall list and see how many supplement companies will SNEAK in medications to make their product effective. And ALL of these companies were caught after receiving COMPLAINTS. Imagine how many are on the shelves with medication in them being taken by innocent people who don’t know?

      I’ll wait. You’ll have DOZENS of pages of recalled supplements, more than half because they contain medication that is not supposed to be in there and is NOT ON THE LABEL. This is just the DANGEROUS list of supplements they FOUND. They don’t recall supplements that don’t work.

      Now I’m sorry, but ALL companies just want to sell products. But I’d MUCH rather deal with a company that is FORCED to PROVE a substance is effective and relatively safe than deal with unknown supplement companies making wild claims of ‘curing’ illnesses with no proof it works and no proof they aren’t DRUGGING IT.

      And I am NOT a fan of Big PHarma either because they price things WAY more expensive then they should be, just to make money. But at least the medications WORK for most people/cats and are SAFE for most people/cats.

      I have saved DOZENS of kittens without lysine too. It’s getting antibiotics when it’s necessary. But I also use saline drops, breathing treatments, humidifiers, fluids, and steroids/antibiotics in really bad cases. It’s about using EFFECTIVE treatments. If lysine ACTUALLY worked, I’d be all for using it, it’d save me a TON on vet bills. But it just doesn’t.

      Also, vets aren’t in veterinary medicine for the money. Check out the price of a human hysterectomy versus a spay surgery for a dog or cat. Vets run a business to earn a living while doing what they love: saving animals. They aren’t in it for the money, just enough money to stay in business and make a living. They do NOT make as much money as SUPPLEMENT COMPANIES do.

  21. Lysine actually helped my cat. He had a bad eye infection that after searching online for the symptoms was herpes in cat’s eyes. After I gave him lysine with his food, his eye started getting better until it completely went away.

      1. This is actually true for cats, who are very sensitive to it. But lysine marketed for cats (or dogs) should not contain that anyway, if it is an ethical company anyway.

    1. Erica,

      I care about cats. I WANT to help people help cats. My goal is the CATS and THEIR welfare, not whether or not I’m right or wrong. I have literally ZERO biases about lysine. If you want to believe lysine is effective regardless of evidence, that’s your choice. I presented evidence in the article, if you want to ignore it, that’s your choice as well. But it’s the CATS that suffer for OUR ignorance when we make mistakes, so I make sure to look at PROOF before I recommend ANYTHING. Helping CATS is my ultimate goal. Their welfare is my #1 priority NO MATTER WHAT. Not avoiding vet bills, not saving money, not making money, not bashing companies, NOTHING else but CATS. My beliefs and opinions CHANGE based on evidence. I don’t ignore evidence to support my beliefs and opinions. So I do a LOT of research so I can BEST help these cats.

      I don’t care if lysine works or not. It’s EVIDENCE that says it doesn’t work. I’m just reporting it to the people who actually care about the cats and evidence. People are always free to believe the evidence. Or not.

      Two problems with your argument:

      1) You don’t actually know it was feline herpesvirus. Eye infections in cats are SUPER common, especially with upper respiratory infections, of which feline herpes is only ONE cause of them. There’s chlamydia, calicivirus, bordetella, and many fungal infections that cause eye issues as well. Not to mention simple bacteria and eye abrasions, tear duct infections, etc. You can’t just Google it and diagnose it. Otherwise, I’d have cancer, according to my symptoms on Google! Diagnosing requires tests, exams, and a veterinarian…

      (What Google is ACTUALLY good for is FINDING SCIENTIFIC STUDIES though! You can search for scientific studies on lysine and actually LOOK at the numbers in these studies where they compare cats taking lysine against cats having NO treatment.)

      If it was that easy to diagnose feline herpes instead of calicivirus then they wouldn’t need to actually send samples to the lab to determine WHICH virus or bacteria is causing the infection. ALL upper respiratory infections in cats HAVE THE SAME SYMPTOMS. My vet only recommends doing lab tests in cases when the common treatments aren’t working because it’s SO expensive. So my vet NEVER ‘diagnoses’ a specific virus for sure unless we run those lab tests.

      So you don’t know 100% what was causing those eye issues unless you got a sample tested at a lab that came back positive for feline herpes. So you don’t know that lysine works on feline herpes if you don’t actually know for SURE it was feline herpes at all.

      2) CORRELATION does NOT equal CAUSATION. That’s why people study things. Anecdotal evidence is NOT evidence. Google anecdotal evidence and you can learn why not.

      But one case of a cat ‘getting better from a mysterious eye infection with unknown cause’ doesn’t prove lysine works. Anecdotal evidence is a CORRELATION between two things. But it does NOT prove CAUSATION.

      Did you know cats get better from upper respiratory infections because of their own immune systems? But you don’t have people running around advocating for people to STOP treating cats because THEIR cat got better by itself. There’s even ONE case of RABIES that got better without treatment. What if that lady started claiming we don’t NEED treatment for rabies because SHE got better without help? Sounds silly, right? But it’s exactly the same thing. Because anecdotal evidence is NOT PROOF.

      For example, Bob had a headache. He drank willow bark tea. His headache was gone! That is anecdotal evidence. Bob can’t PROVE willow bark tea was the cause of his pain relief. He just has a THEORY that willow bark tea cured his headache.

      Bob was logical enough to know that other things could have made his headache better or it could have gotten better on its own, so Bob decided to do an experiment to PROVE his theory. Bob conducts a study where he gives willow bark tea to 10 people with headaches and he gives 10 other people with headaches green tea and TELLS them it’s willow bark tea. These 20 people were carefully monitored so they were SURE they didn’t take ANYTHING else. No one knows who is taking the REAL ‘medicine’ except the scientists. Then he asks everyone at the end if their headache is gone.

      The group of people who took willow bark tea reported that 9 headaches were gone! The group that took green tea reported only 3 headaches were gone. See where I’m going with this? Therefore, WOW, willow bark tea helps with headaches! (It actually does, willow bark is where aspirin was discovered!). But those 3 people who reported headaches getting better in the green tea group? It doesn’t mean green tea helps with headaches. It just means they either “got better on their own” (which happens) or “they THOUGHT it was going to work so it DID work” (the placebo effect) or that “green tea MIGHT be effective at headache relief but NOT at effective as willow bark tea” (possible, certainly, but more studies needed to determine whether this is true or not.)

      That’s exactly what happened in lysine studies. They took 2 groups of cats, ALL of them TESTING POSITIVE for feline herpesvirus. So they could tell for SURE they had the right virus. They gave one group of cats lysine. They gave the other group of cats NO lysine. Both groups took NOTHING else. And BOTH groups had the same number of cats get BETTER. It was about 30-40% I believe, but don’t quote me on that as there’s been quite a few studies on it. So guess what? Lysine helped JUST as many cats as the NO TREATMENT group did!

      So why would I waste money on lysine for upper respiratory infections that I can’t even prove ARE feline herpes viruses without testing the cat with expensive lab work? Apparently, NOT treating the cat works just as well as lysine anyway!

      Did you know Clavamox, an antibiotic for cats and dogs, was proven to cure symptoms of feline herpes virus in 100% of the cats in a study on lysine? Yup, totally true! The lysine study ended up proving that CLAVAMOX was a better treatment than lysine.

      But y’all can spend as much money as you want on lysine. You can believe your anecdotal evidence if you want. It is no skin off my nose. If you’re so dead set pro-lysine that you’ll turn a blind eye to ALL evidence against it available in multiple studies available online, you’re free to do so.

      Willful blindness only hurts the CATS. So I make all efforts to be as unbiased and open to evidence as humanly possible and am always willing to change my opinion if there is EVER new evidence to come out that lysine is effective for ANYTHING.

      But the ONLY evidence available says lysine does NOT work.

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