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What causes my cat's recurring rodent ulcer and swollen lip?

Updated On September 23rd, 2025

Pet's info: Cat | Siamese | Female | spayed | 1 year and 10 months old | 10 lbs

My cat has Rodent Ulcer that comes back every so often and I have had her for about two months. Before I adopted her they warned me to watch if it comes back and it did. They said the cause could be from stress or allergies, I found the Authority Sensitive food and she seemed to be okay with it and I mixed E.Colloidal Silver with wet food (same brand) to help her. It went away 2 weeks later and I recently switched her wet food and it looks like her lip is starting to swell. What is the cause?

3 Answers

Most Helpful Answer

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Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on August 2nd, 2018

Rodent ulcers, or eosinophilic granuloma complex, are typically allergy related. Identifying and treating the underlying allergy is the foundation for treatment. Have Sophie examined by your veterinarian. Discuss allergy testing, hydrolyzed diets and food elimination trials. Your vet can dispense or administer steroids to decrease inflammation and antibiotics to treat any infection.

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    Answered By Dr. Davis

    Veterinarian

    Published on April 17th, 2018

    Unfortunately the photo did not come. The most common lip problems in cats are eosinophilic granulomas. They cause a red, ulcerated thickened area in the lip, usually the lower one. The treatment usually includes a long acting steroid injection. These can recur and are thought to be immune mediated or caused by stress. Please try to resend the photo if this description isn’t what you are referring to. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Leo.

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    Answered By Jenna Beyer, DVM, MBA, cVMA

    Veterinarian, Certified Veterinary Acupuncturist

    Published on November 5th, 2017

    It does sound like she has a Rodent Ulcer, also known as Eosinophilic Granuloma Complex. They can seem to wax and wane as far as severity, and sometimes get better with no treatment at all. If they get very bad, often steroids or other immune-modulating medications can be helpful. I would recommend that you talk to your vet about a hypoallergenic prescription cat food or a food trial since there is some thought that there is an allergic component to these ulcers. Here is some more helpful information: http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=656

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