How do cats get cold sores?

Updated July 19, 2017

Cold sores are painful and annoying, even for cats. They are caused by the feline herpes virus and can affect any cat during any point in its life. Feline herpes is a recurring disease that once contracted has no cure. Cold sores are unpleasant and chronic, but not lethal.


A cat must come in contact with the herpes virus and become infected to get cold sores and the virus isn't airborne. Contact can occur by rubbing or licking another cat during a herpes outbreak or touching a surface that is covered with the virus, such as used food containers, litter boxes and toys. Cats cannot contract or give the virus to humans.


After an initial herpes infection, the cat will seem like he has a cold and will eventually get tiny blisters around his mouth that burst and turn into grey ulcers. Runny noses, sneezing and constipation are all common first symptoms. Alone these merely point to herpes and are not proof. Conjunctivitis causes the clear covering over your cat's eye to get cloudy and is a tell-tale sign of herpes.


There is no cure for herpes and recurrence is inevitable. The symptoms will be the same as the initial outbreak, but often less severe. The cat's immune system now fights off the infection, making each subsequent outbreak similar, but less severe than the original. Poor sanitation, stress, fleas, a poor diet or another illness can all trigger an outbreak.


Cold sores and other symptoms of herpes are manageable during an attack. The most common treatment is an antiviral eye drop that helps alleviate the cloudy, watering eyes. Keeping your cat warm and clean, and substituting strong smelling foods like sardines, can help with the flu-like symptoms and lack of appetite. Never use human herpes treatments, which adversely affect the cat.


Cat herpes is really hard to prevent, especially in outdoor cats. Keep food containers and toys clean and disinfected to reduce amounts of the virus. Watch out for neighbourhood cats that may already have the disease. If you do know a cat has herpes, don't allow your cat near it during an outbreak and watch out for toys or food containers they might share. Unvaccinated and sick cats are more prone to infection, so healthy cats are less likely to get cold sores.

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About the Author

Based in Seattle, Robert Bettington first began writing for his high school paper in 1993. He then wrote for “Mustang Psychology” while in college, contributed to “Central Coast Green Magazine,” and edited “Stuck,” a novel by George Basil. He received his Bachelor of Science in psychology from California Polytechnic University in 2000.