Is L-lysine good for herpes virus in cats?

In other words does L-lysine help domestic cats control the feline herpes virus which is very prevalent in cat rescue shelters and catteries? The feline herpes virus is one of two which causes cat flu. The other is calicivirus. The virus can lay dormant and flare up under stress. During these flare ups vets sometimes recommend L-lysine to decrease viral reproduction.

Lysine is an essential amino acid. L-lysine has many supporters perhaps among cat breeders and people involved in caring for many cats. Research on humans suggested that large amounts if this amino acid inhibited human herpes virus in cell cultures (artificial growth of cells in an ideal environment).

I wrote the following years ago about this product (this is a shortened/amended version):

“…I noticed that a number of cat breeders use a food supplement called L-lysine. Experienced cat keepers and breeders say it can control the feline herpes virus. Users of one particular brand of Lysine, Duralactin Feline L-lysine, say that it is one of the best ways to control herpes, both feline or human.

One purchaser of this product, who looks after “special needs cats” suffering from herpes says that “when there is more lysine (and therefore a greater proportion of lysine compared to arginine), viral replication is suppressed and cytopathogenicity (pathological changes in cells) is inhibited”.

Duralactin Feline L-lysine is apparently very attractive to cats. They love the taste of it; so no problem administering it. A well known Bengal cat breeder simply buys lysine products made for humans in capsules and crushes them with a spoon and sprinkles the powder on cats food.”

In the intervening years since I wrote this, science has become more familiar with L-lysine and it efficacy or otherwise in controlling the dreaded herpes virus in cats.

Sadly it is bad news for L-lysine fans. The website reports (August 2014) that L-lysine is ineffective in suppressing herpes virus reproduction.

“[there is] little justification for the use of L-lysine in the treatment of feline herpesvirus 1 in cats.”

The research which came to this conclusion ‘corrected some of the technical flaws in the original research’. The recommendation is to ask your vet for alternative treatments if your cat is on L-lysine.

I suspect that many cat owners will ignore the findings of this research because they have first hand experience of the successful use of this product. Do you?

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Useful tag. Click to see the articles: Cat behavior

12 thoughts on “Is L-lysine good for herpes virus in cats?”

  1. For the first 10 or so years of my 19-year-old kitty’s life, he had sores on his mouth on a regular basis that were caused by the herpes virus. I started giving him L-lysine on a daily basis at the recommendation of an eye specialist after he developed plaque on his eye, also a result of the herpes virus. He hasn’t had mouth sores or plaque on his eyes since. He still gets the “kitty colds” that occur if he goes through something stressful (a trip to the vet will do it), but I just increase the dosage of L-lysine and it goes away in about a week. I wouldn’t dream of not giving it to him at this point.

    1. Great comment Steph F and many thanks. It does not surprise me that the ‘evidence’ of real cat owners differs to that of scientists in studies.

  2. I use the lysine powder (human form bought through Amazon), and I definitely notice the difference. I have a larger number of cats (think sanctuary), with 4 of them being FIV+. The FIV+ cats seem to get less colds or URIs when they are on it. I dilute it into their drinking fountain water as it has no taste or smell. Tried it myself first to make sure. The Lysine treats did nothing, they were junk as far as I’m concerned.

    1. Many thanks Nikki. Nice information. Useful. It does not surprise me that people who know cats and who use L-lysine find it a useful treatment.

  3. I absolutely swear by the stuff. I sprinkle it (plus a probiotic ) on the kitties wet food. I have seen improvement in overall health plus a decrease in sniffles.

  4. Yes we use l-lysine powder which was recomended to us by several vets 20 years ago . A recent group of kittens diagnosed with Herpes was put on antiviral drugs and l-lysine 2 weeks ago.

  5. Roslyn Stoddard

    I have some and have some and have used l-lysine in the past for uri’s, but I’m not really a fan. Have not seen any significant improvement with its use.

  6. Elisa Black-Taylor

    We use l-lysine for skin conditions. A few of our cats get what the vet nicknamed “the crusties” and the l-lysine helps a lot. Where the cats used to need 4 allergy shots a year for them they only need 2 now. As far as URI’s go it hasn’t seemed to help but since we’ve started feeding grain free food the URI’s have all but ceased.

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