Often when someone says their cat has an upper respiratory infection, they are advised by friends who have had cats for years that they should sprinkle some lysine on the sick kitty’s food. However, a look over the body of research available indicates that lysine supplementation does not help cats with Feline Herpesvirus (FHV-1).
What is Feline Herpesvirus?
Feline Herpesvirus (FHV-1) is one of the main causes of upper respiratory infections in cats, and it is directly or indirectly accounts for over 90% of feline eye diseases. The virus is very common, and many cats are exposed to it as kittens by an infected mother caring for them.
The virus transmits between cats through:
- Direct contact through saliva or through nasal or eye secretions
- Inhaling sneeze droplets of an infected cat
- Sharing food bowls and litter boxes
- Sharing contaminated bedding or grooming aids
FHV-1 Infection Symptoms
At the time the cat is infected, the main symptom of FHV-1 is an upper respiratory infection, including discharge from the eyes and nose, sneezing, fever, lethargy, and sometimes coughing.
After the upper respiratory symptoms are gone, the virus remains in an inactive status in the nerve cells of most cats. A little under half of those cats will have the virus reactivate at some time later during their life. The FHV-1 virus reactivates when the cat is under stress, including emotional or physical stress. Additionally, some drugs like corticosteroids are likely to reactivate latent FHV-1 in a cat.
When the virus reactivates in a cat, the cat might show upper respiratory symptoms mentioned above, or the kitty might instead only shed the virus, becoming contagious to other cats without appearing sick.
Less commonly, cats with chronic FHV infections have inflamed corneas (the clear covering of the eye) that can lead to ulcers in the eye.
Why Do People Expect Lysine Would Help with FHV-1?
Dr. Andrew Weil, an integrative physician for humans, recommends that people with the viruses that cause herpes in humans, HSV-1 and HSV-2, reduce the amount of the amino acid arginine in the diet and increase their intake of the amino acid lysine to reduce symptoms. There is mixed evidence about this, practice, but it is frequently repeated advice both around the internet and through veterinarians.
The theory behind this is that lysine interferes with the replication of the virus by blocking the body’s uptake of arginine, which can worsen herpes outbreaks. Human bodies create arginine naturally but require dietary lysine, so dietary modifications and/or supplementation are suggested.
Cats, Lysine and Arginine
Cats and humans aren’t the same. An overview of all of the previous research done on lysine and FHV-1 showed that lysine does not inhibit arginine in cats. This means that there isn’t really a purpose behind supplementing cats with lysine.
Unlike with humans, cats don’t create arginine. Finding ways to reduce arginine in their diet isn’t necessarily beneficial because arginine deficiency can result in excess ammonia in the blood, a condition that can be fatal.
The evidence found that orally supplementing cats with lysine was not effective and in some cases can enhance FHV-1 viral replication, making infection worse.
Belief Perseverance
When this research first came out last year, internet discussions about it tended to say, “I have seen kittens get better when supplementing them with lysine, so I will continue to give it to sick kittens.” Comments on articles dismissed the research instead of looking more closely at it to see if maybe their perceptions of it had been flawed.
Maintaining beliefs and theories against explicit conflicting evidence isn’t unusual. The psychological phenomenon actually has a name: belief perseverance. Behaviors we think are beneficial are especially hard to break, but over time, this may change in the face of the evidence that cat physiology doesn’t work like human physiology.
Do you think that one day, giving cats with upper respiratory infections lysine will be like feeding cats milk is today: a practice that used to be common and is now considered old-fashioned?
Research and further reading
Bio Med Central, Lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats: a systematic review
International Cat Care, Feline herpesvirus (FHV) infection
Michigan Veterinary Medical Association conference proceedings, FHV-1, Can One Virus Cause All Those Diseases?
Journal of Nutrition, Excess Dietary Lysine Does Not Cause Lysine-Arginine Antagonism in Adult Cats
Image credits
Creative commons images courtesy flickr/pmarkham, kayveein
depositphotos/designer491, funny_cats, belchonock
Interesting! I’m more interested in finding out what works instead of lysine, now that its effectiveness is being questioned.
Us too.
Try lactoferrin. Very effective. Good for immunity also.
Try lactoferrin. Very effective. Good for immunity also.
My goodness what very valuable information.
Hugs and Happy Monday
Madi your bfff
This was very interesting – but it’s Mum that has the problem not us!
Thanks for this information. We have heard that using lysine in cats is not very helpful. Fortunately none of us have the herpesvirus.
Very interesting…I’ve also heard that lysine is beneficial for a healthy immune system in general. I wonder if that’s being called into question as well?
Yup its not true (doesn’t help immunity). Try lactoferrin. Very effective. Good for immunity also.
Interesting post. I know people who are die hard Lysine believers. I’m going to check out the research, it’s probably an interesting read since I was told Lysine works. I’m also curious about what works instead.
Nicely offered info. I love you offering the concept of belief perseverance– important lens to view medical advice for 2 and 4 legged! Thank you.
Excellent post. I fell for that too with my Polar Bear and nothing helped. He is just always going to be sneezy, when it seems like he has an infection, I get him antibiotics.
Is there something that works?
Mom stopped using the Lysine about a year ago since it had no effect at all. Ellie gets bouts of “the sneezies” and Mom gives her low doses of doxycycline which seems to help.
Like Summer, we wish we could find something better that works.
The Florida Furkids
I am just glad that I am no longer hearing that lysine boosts immunity. that always made me scream. (watch, now that I’ve said that I’m going to run into ten people who believe it)
This is very interesting! Do you think there are any benefits to giving cats lysine, even if it doesn’t help with URIs?
guys…bye noe meens due we understand ANY…. chemical stuff…..
but de old site we used ta bee on had manee bee leevers in L-lysine
for kittehz…whether L-Lysine iz mor effective than lysine; we troo
lee due knot noe; we R knot even sure if itz de same “thing”
we R thanx full we never kneaded ta try…..either
🙂 ♥♥♥
Fascinating and well done posting.
Thank you for sharing it.
Many years ago my Dad’s Mom had a kitty with Herpesvirus and that stuff really seemed to keep it under control. Great post.
It seemed to me that Lysine was a cure-all. I’ve seen it mentioned to cure lots of things including my asthma. Thanks for the facts.
You rock.
Changing something embedded as “conventional wisdom” is like trying to steer the Titanic around an iceberg. Hopefully science will manage to slowly penetrate the ranks. Of course, we’ve also seen studies reverse their findings, or have too small a sample size.
Though this study sounds like hard science vs. softer science studies that study empirical evidence of patient response….
What a great and informative post, thank you!
Interesting! I know a lot of people in rescue who use lysine as a kind of cure-all. And I have a five-year-old cat with chronic eye problems as a result of a kittenhood herpes infection (nope, lysine did not help), so I, too, would be interested in knowing if there is anything that IS effective. The vet and I have tried everything under the sun, it seems, and nothing makes any difference. Thanks for this post!
I have heard this for many years and had no idea of rhe new research until seeing this post, thank you for sharing the information. Belief perseverance is one of the biggest obstacles in animal rescue when it comes to health, breed specific legislation, black cats, FIV cat adoption, and so much more. What continues to baffle me is seeing normally intelligent, devoted people who continue to balk, fight against scientific research. I hope more study is done on the subject and that people keep informed with an open mind.
Very interesting article. I had read about using lysine a few years ago and the doubts as to its effectiveness. Some people at the local shelter swore by it to help treat/prevent URI in the shelter kitties. Whether it worked or not, I think they felt is was a relatively inexpensive way to do something they thought might kelp the kitties.
I have given lysine supplements to Raven, who carries upper respiratory virus & has issues when she’s stressed. I’ve not seen any evidence that they work and I know that’s completely anecdotal evidence. But it’s one of the few treats she enjoys, so I still give them to her occasionally. I doubt I’ll buy more when these are gone.
Belief perseverance is very difficult to overcome. Despite overwhelming evidence to the contrary, people are still convinced poinsettia plants will kill their pets and refuse to have one in the house.
There is no cure for herpesvirus infections. The therapeutic goal is to reduce the frequency and severity of recurrences. Most cats respond well to medical management of the condition and lead normal lives. Minimizing the chance of infection, feeding a premium diet, supplementing the diet with l-lysine daily, reducing stressful situations and following an appropriate vaccination schedule are your cat’s best defense against this disease.
my kitten has been through. thorough tx of herpes virus and giardia, he has excellent energy levels and appetite is improving daily he continues with fits of sneezing as well as loose stool, now i have develop sx of uri .literature states the herpesvirus is not transferable between cats and humans how reliable is this?
I have to disagree that the research shows that lysine doesn’t help. Having read as many research papers as I could get my hands on, it seems to me that we simply don’t know. The number of studies is small and the N’s were tiny. Furthermore, some of the papers I read DID find a benefit in lysine treatment, but the differences between treatment and placebo didn’t rise to the level of significance.
The conclusion that lysine doesn’t help comes from the Bol and Binnik paper – and that was a small meta-analysis, not a scientific experiment. I believe that meta-analyses can miss trends, especially when the studies reviewed had tiny N’s, and when the subjects in different studies have different characteristics.
An example would be a meta-analysis of moderate carbohydrate intake on diabetes risks. If you look at the North American population as a whole, you’ll miss the fact that some Native American tribes developed astonishing rates of diabetes when they adopted European diets.
I don’t have access to the full Bol and Binnik paper, so all I can base my conclusions on is their abstract. They don’t cite the authors or give N’s in the abstract.
I looked for clinical and in vitro research for the effects on the virus. There isn’t a lot, it is old, and the numbers of subjects are really small. But of the papers I found, some beneficial effects of lysine were noted. See Maggs et al. (2003) and Stiles et al. (2002). But because of small sample sizes, made smaller by the number of cats with serious symptoms, the differences didn’t rise to the level of statistical significance.
That is NOT the same thing as saying there is no benefit. My take is that we just don’t know whether lysine helps; the research hasn’t been good enough.
Some of the in vitro work was even more concerning. Some researchers dealt with different cytokine and T-cell differentiation levels – and it appears that they don’t have a global understanding of the mesh of cytokines and how T-cell differentiation might impact Feline Herpes. Blanket statements were also made about individual cytokine levels that may not actually be relevant to disease. So IL-4 increases T-cell differentiation and IL-10 acts as an anti-inflamatory agent. What does that mean for feline herpes virus? What about the plethora of other kinds of cells in an immune response? I also wondered at some of the claims when I looked at the actual data tables.
It’s clear that we need more money in veterinary research, to fund decently-sized experiments.
Thank you for the effort you put into researching more about the effects of lysine on FHV!
For anyone who wants an alternative that actually works, try lactoferrin. Very effective and good for immunity also. https://www.rawfeedingforibdcats.org/uri–herpes-management.html
I highly recommend. 👍
Eliminate (Herpes)..with herbal Med…🍃🍁🌿🍂
The best online,
He brought my Ex lover back…….
Fix all relationship/marriage problem…
[ R.buck ler1 1 ‘ ‘ @g ma i l… c o m ],……….