Can Lysine for Cats Help With Illness?
Lysine for cats is often recommended as a way to boost the immune system and lessen upper respiratory symptoms such as sneezing, congestion, and runny or red eyes. But while lysine supplements are readily available over the counter, they shouldn’t replace modern medicine.
If your cat is experiencing respiratory symptoms, schedule a vet appointment. They may need medical treatment lysine can’t provide. You also shouldn’t give a cat lysine without speaking with your veterinarian first. Lysine should NEVER be given as a replacement to traditional medication.
Here’s what to know about giving your cat lysine—and if it’s effective.
What Is Lysine?
Lysine, or L-lysine, is an essential amino acid. Amino acids are the building blocks of proteins in the body. Cats generally get all the essential amino acids they need to maintain good health from a specially formulated cat food, so lysine supplementation is rarely necessary for a balanced diet.
Lysine is not an FDA-approved supplement for use in cats, so its use in veterinary medicine is off-label. Though the governments in other countries, such as Canada, highly regulate supplements to ensure they provide the benefits the product claims on its label, these substances are not heavily regulated in the U.S.
What Does Lysine Do for Cats?
In cats, lysine is thought to slow down the replication of feline herpesvirus-1 (FHV-1). FHV-1 in cats is also called feline viral rhinotracheitis. It’s a very common virus in kittens that causes cold-like symptoms such as sneezing, nasal discharge, eye discharge, and conjunctivitis.
FHV-1 depends on arginine (another amino acid) to be able to replicate inside a cat's body and cause disease. When a cat takes a lysine supplement, the lysine coats the herpesvirus. This prohibits arginine from replicating the virus.
Without viral replication, the symptoms of the FHV-1 virus are thought to lessen or even resolve.
Does Lysine for Cats Work?
Unfortunately, there is conflicting information as to whether giving a cat lysine will help with respiratory health. Veterinarians have historically recommended lysine for cats to help combat the effects of FHV-1. But in recent years, there have been numerous studies determining lysine is not effective in preventing or treating FHV-1 in cats.
Under experimental conditions, lysine was able to decrease the amount of viral shedding, thus decreasing the chance that FHV-1 would spread to other cats. However, in recent studies of natural infections of FHV-1, lysine was shown not to be effective. In fact, lysine may actually increase the amount of viral shedding and cause FHV-1 symptoms to get worse.
In one study of shelter cats, 144 cats received lysine every day while 147 did not. Between the two groups, there was no difference in how many cats developed conjunctivitis or an upper respiratory tract infection (URI). This suggests lysine is not able to prevent respiratory illness in a shelter setting.
Lysine for Cats Side Effects
There are no known side effects of lysine supplements for cats. In humans, lysine can cause abdominal pain and diarrhea.
Should I Give My Cat Lysine?
Lysine is an over-the-counter supplement for cats, so you don’t need a prescription to give it to your kitty. If you are considering giving your cat a lysine supplement, it's extremely important that you discuss this with your veterinarian first. Stress is common when trying to medicate cats, and any stress can exacerbate a virus like FHV-1.
How To Give a Cat Lysine
Lysine supplements for cats come in many forms, including powders, pastes, gels, treats, or capsules. You can add the powder, gel, or contents of a capsule to your cat’s food or a treat to make administration easy. Most of the lysine treats are extremely palatable and your cat should eat it by itself.
Again, talk to your veterinarian before giving your cat lysine. If your cat is experiencing symptoms of a respiratory illness, lysine is likely not the appropriate treatment.
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