Lysine Therapy for Cats

Lysine can help clear up eye infections due to herpesvirus.
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The feline herpesvirus is one of the most common and contagious viruses in cats. It causes upper respiratory and eye problems, and once Kitty has it the virus is there for life. Supplementing with lysine reduces recurrence of symptoms and helps keep him healthy. Ask your vet about lysine therapy.


The amino acid lysine, also known as L-lysine, helps produce collagen, leading to a healthy skin and coat in Kitty. Cats can't produce this particular amino acid in their own bodies, so they need to consume it. Naturally, it's found in various types of meat, and cats are obligate carnivores. That means they must eat meat to survive. Lysine also fights the herpesvirus, so your vet might recommend supplementation if that's a chronic problem for your cat.

Feline Herpesvirus

While feline herpesvirus can affect any cat, it can be deadly in kittens and cats with compromised immune systems. As the name implies, it only affects felines. Cats pick up the virus from contact with the bodily fluids of infected animals, usually coming down with symptoms within a few days. Feline viral rhinotracheitis results, with sneezing and a stuffed-up nose. It's often accompanied by conjunctivitis, inflammation of the white membrane around the eye and inside the lid. Cats may blink excessively, along with a clear or colored eye discharge. If you find kittens with gunked-up eyes they can barely open, herpesvirus is the likely culprit. While your vet might prescribe other medications to fight the infection, lysine can help keep it at bay.

How It Works

When you supplement with lysine, that amino acid makes the herpesvirus use it instead of the arginine, another amino acid, when it replicates. However, the lysine actually destroys the herpes virus. Not only is there less herpesvirus inside Kitty, but many, if not all, of the clinical signs of infection disappear. The eyes of cats with herpes-related conjunctivitis should clear up, while those affected with upper respiratory symptoms should stop sneezing and wheezing. A 2003 University of Missouri study using lysine and steroids in cats infected with feline herpesvirus concluded: "Once daily oral administration of 400 milligrams of L-lysine to cats latently infected with feline herpesvirus was associated with reduced viral shedding following changes in housing and husbandry but not following corticosteroid administration."


Although you can give your cat the lysine pills sold over-the-counter for people if the dosage is correct and your vet OKs it, you're better off purchasing lysine supplements made just for cats. Your vet might have these non-prescription formulas on hand, or you can purchase them at pet stores. Rather than pill your cat -- never a pleasant experience for either of you -- try a flavored gel that you can put directly into his mouth or wipe on his paws for him to lick off. Lysine treats are also available, so you can supplement Kitty while he thinks he's getting something special. Powdered lysine you can mix into his food is another alternative.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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