Two Easy Ways to Start Earning Rewards!
Become a member today!
Members-only pricing and offers, personalized care notifications, Vital Care points back on every purchase and more!
Already a member? Sign in
Become a credit card member today!
Earn 2X Pals Rewards points at Petco
when you use Petco Pay!
APPLY NOW
Learn More About Petco Pay Benefits

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

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.

1Pet Parents found this answer helpful

Related Answers from Veterinarians

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.
1Pet Parents found this answer helpful
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
1Pet Parents found this answer helpful

Smart Picks for Smart Questions

Related Questions

Why does my cat have a lip sore? Is it a rodent ulcer or allergy?

This appears to be what is commonly referred to as a 'rodent ulcer'. The most common cause for these to pop up in cats is an allergy, typically to something in the food. Sometimes these will resolve in their own, however sometimes they can become infected, long lasting, and problematic. If they become very large and painful it can discourage the cat from wanting to eat. If this ulcer has been present for more than 2 weeks it is probably not going to go away on its own. At that time I would recommend taking you cat to the vet for treatment. Nathaniel may need antibiotics and an immunsuppresive drug like steroids or Atopica. If the lesions keep coming back he may need to be on an immunosuppressive long term and/or a hypoallergenic diet. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck.

Updated on September 23rd, 2025

My cat has rodent ulcers, swollen mouth, flea allergy. How can I help?

Poor Sedrick. Most cats with rodent ulcers and severe allergies like this need antibiotics and steroids to heal. I would have your vet take a look at him. Your vet will be able to prescribe him the appropriate medicine to help him feel better. If you don’t think you can give pills, talk to your vet about an injectable options as there may be an antibiotic and steroid available so you don’t have to treat at home. Also make sure you start I’m on a high quality flea preventative like comfortis, cheristan, or advantage multi. Fleas also live in the environment so make sure you treat your house and yard for fleas as well. I hope this helps.

Updated on September 23rd, 2025

Health & Wellness

Why does my cat have swollen lips and keep sneezing? Is it serious?

This looks to be a rodent ulcer (eosinophilic granuloma complex). She really needs to see a vet for this issue. This is not something you can treat with over the counter medications. Also, there are not many over the counter medications that are safe for cats. These lesions are treated, typically, with antibiotics and steroids. Likely the reason for it is hereditary or an underlying allergy. Please refer to this article for further information. ( https://www.thesprucepets.com/rodent-ulcers-in-cats-5093328 ) The sneezing is not likely related to the swollen lips. That seems to be a separate issue. Either way, Luna needs to see a vet.

Updated on September 23rd, 2025

My cat's mouth sore won't heal. What could it be and what to do?

I'm so sorry that you are dealing with this with Vivian. The location is a little abnormal for a rodent ulcer, so I would probably recommend more dermatology diagnostics (especially in an 11 year old cat if she hasn't had problems with this before). That may include a skin scraping or cytology of the area or even a biopsy of the area. Sometimes challenging skin problems require a referral to a veterinary dermatologist for a diagnosis. You can find a veterinary dermatologist near you here. https://www.acvd.org/tools/locator/locator.asp?ids=16_Find_Dermatologist If all results still point to a rodent ulcer, there are other medications you can try that will suppress the immune system. I have included more information on feline eosinophilic granuloma complex below. https://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=656 Good luck! I hope that was helpful. Thanks for using PetCoach.

Updated on September 23rd, 2025

Health & Wellness

My cat's lip is swollen. Is it an allergy or something serious?

From the photos it looks like Xena has a "rodent ulcer" (aka: eosinophilic granuloma complex). It is best to have her checked out by your regular veterinarian to get a definitive diagnosis and treatment. ( https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4951528 ) Hope this helps. Best wishes.

Updated on September 23rd, 2025

My cat has a swollen bottom lip with acne. What could it be?

This condition is called Eosinophilic Granuloma Complex , also known as "rodent ulcer", The exact cause of feline eosinophilic granuloma complex is unknown. Some research studies suggest that a form of allergic response (hypersensitivity reaction) may be involved in the majority of cases. This is more likely in cases that are recurrent. Other studies suggest that the condition may at least be partially genetic or inheritable. Flea and insect control is very important in the treatment of feline eosinophilic complex. This is due to the suspected hypersensitivity reaction cause of the condition. Insect bites can trigger an exaggerated immune response in affected cats, causing or worsening clinical signs. Some cats respond to elimination or hypoallergenic diets, suggesting an underlying food allergy as the cause. Most cats diagnosed with feline eosinophilic granuloma complex benefit from a hypoallergenic food trial. Corticosteroids are the most common treatment to control the symptoms of eosinophilic granuloma complex. you will need to visit your vet to get this treatment.

Updated on September 23rd, 2025

Food & Nutrition

My cat has a recurring rodent ulcer. Should I try lysine or omega?

Poor Vivian! Unfortunately rodent ulcers are usually an auto-immune issue. I certainly think lysine and omega 3 fatty acids are beneficial long term. Vetriscience has some good products for both of those. I would also consider a veterinarian prescribed hypoallergenic diet. I am not sure colloidal silver will help. Some of these guys end up needing multiple steroid (+/- antibiotics) injections throughout the year to keep it under control. If it doesn’t start to clear up I would consider another steroid shot. Cats usually tolerate them well every 6-8 weeks. I hope this helps.

Updated on September 23rd, 2025

Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Share