Causes of Feline Mouth Sores

James Glover
by James Glover
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QuestionMy cat has sores in its mouth, usually one at a time, and it has been continuing for about a week or so. The sores are on the lip and inside of his mouth and I tried putting rubbing alcohol to clean them but they start bleeding. I though it was a spider bite at first but its continuous. What could it be? (lauren tucker - Washington)


I always recommend that you take your pet to your veterinarian if you notice any unusual symptoms. In this case, it is specifically difficult to suggest a diagnosis without a thorough examination. There are two common reasons for mouth sores in cats - viruses and irritants.

A virus called calici affects the mouth, eyes and sometimes lungs of a cat and nearly always results in mouth sores. In normal circumstances there would be multiple sores spread across the tongue and lips, and would be accompanied by other symptoms such as nose or eye discharge and loss of appetite. Calici infections must be treated early as they can lead to complications such as pneumonia. The other possible viral cause is the feline herpes virus, but this also usually results in eye or nose discharge.

The other possibility is that your cat has come in contact with an irritant, which can include toxic plants, toads, cleaning fluids and anything else that can cause irritation. Does your cat have access to parts of your house or garden that he did not previously? Have you started using a new household cleaner? Do you have any new plants in your house or garden? If you answered 'Yes' to any of these questions it is possible that your cat is displaying a reaction to an irritant. Your vet will be able to suggest further possibilities.

Disclaimer: This service is meant to provide advice only and is not meant to replace an appointment with a registered veterinarian. Users should always seek a second opinion. Unfortunately we are only able to answer several questions per week so not everyone gets a published answer. And, unfortunately we can't answer by email.
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Added on March 24th, 2011
Hey guys! i struggled with the cold sore looking thing on my cat's mouth for months. Vet tested it and said it was bacteria. I had read that plastic bowls hold bacteria even if they look clean and EVEN if you feed them dry food. i changed their water daily already so figured it might be the bowl itself. I bought stainless steel bowls -- problem solved... sore healed completely within a few days and has not come back.
My brother's lab had the same trouble. i shared my experience, they tried new bowls...bam! same thing. dog healed very quickly after having this sore for nearly a year.
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Added on Jan 18th, 2010
My cat had a sore (red, golden crusts at times, clear fluid/serumy wet looking) that wouldn't heal and it turned out that it was an 'eosinophilic plaque'. A shot of cortisone made it go away. Sounds like your kitty probably needs to see a vet.
New York
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Added on Oct 30th, 2008
Why would you even think of putting alcohol in your cats mouth ? Would you do that to yourself ?