Cat Ulcer on Tongue & Lysine

A vet may prescribe Lysine for your cat if she has a tongue ulcer.
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Feline herpes virus and calicivirus are the most common causes of tongue and mouth ulcers in cats. Lysine is typically prescribed for these viruses. However, ulcers on your cat’s tongue may also be a symptom of an allergy, cancer, or another serious illness. While lysine may be the primary treatment for the illness causing your cat’s tongue ulcers, she should see a veterinarian right away for proper diagnosis and full treatment instructions.

Feline Calicivirus

Ulcers on the tongue and roof of the mouth are very common in feline calicivirus (FCV). Cats with FCV may benefit from taking lysine, but often need other medications and treatment. FCV causes upper respiratory infection (URI) and a recent mutation has created a strain called virulent systemic feline calicivirus (VS-FCV) which can cause organ failure and is fatal in about 60% of cases. However, most cats with standard FCV recover well with proper treatment.

Feline Herpes Virus

Lysine is the standard treatment for feline herpes virus (FHV). Despite the name, FHV is not sexually transmitted, and cannot be contracted by humans. FHV typically manifests with cold-like symptoms and can cause ulcers on the tongue. It is also highly contagious and very common in cats. Lysine inhibits reproduction of the virus inside your cat’s body. In some cases, lysine is the only treatment necessary, but some cats require antibiotics to prevent or treat secondary bacterial infections. Severe cases of FHV may require hospitalization.

Upper Respiratory Infections

Tongue ulcers are a common symptom of URI in cats. FCV and FHV are the most common causes of URI, but there are also bacterial forms of URI, and URI can be a combination of FCV or FHV and a bacterial infection. Lysine is part of the standard treatment protocol for cats with URI symptoms. Because URI is very contagious, cats with URI must be isolated from other cats to prevent the spread of infection, even if the healthy cats have been vaccinated against FCV and FHV.


Lysine, also called L-lysine, is a naturally occurring amino acid. In FHV, lysine works by interfering with the virus’s ability to replicate itself. In other conditions, lysine is believed to work by boosting the immune system. Lysine comes in a flavored paste, specifically formulated for cats. You can also purchase it over the counter in capsule or powder form packaged for humans, but you must talk to your vet about proper dosing. Never give your cat a lysine product containing propylene glycol.

Talk to Your Vet

Lysine should only be used under veterinary supervision. Ulcers on your cat’s tongue may be a sign of a condition for which lysine is not appropriate, or a very serious illness, such as cancer, which needs immediate medical intervention. Although Lysine is generally safe, it may cause adverse reactions in some cats and it can interact with some medications. Always consult an experienced veterinarian regarding the health and treatment of your pet.

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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