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Rodent Ulcers: Sores on a cat’s mouth from an allergic reaction

The Patient

Mushroom, an adorable 7-year-old male kitty came in to see me a few weeks ago because he had some sores near his mouth.  When I examined him, I saw red, raw, ulcerated areas on both sides of his lips and another big oval one on the roof of his mouth. Mushroom was rather offended when we had to gently pry his jaws apart to see the problem, probably because the sores were painful. I suspected rodent ulcers.

Our poor patient suffering from rodent ulcers
Here is Mushroom enjoying the breeze.

The Diagnosis: Rodent Ulcers

I diagnosed Mushroom with rodent ulcers or, more medically speaking, eosinophilic granuloma complex.  An eosinophil is a type of white blood cell that rushes to the rescue when there is an allergy in the body and they come out in big numbers to fight it. If we had biopsied Mushroom’s sores, we would have seen many eosinophils under the microscope. The eosinophils are reacting to something that they perceive as foreign in the body, and the gathering of these cells is called an inflammatory reaction. It is this inflammatory reaction that can be itchy or painful to the cat.

Cats can get these kinds of sores anywhere on their body, but on outer skin it usually looks like a thickened line of bumps. They are only referred to as rodent ulcers when on the mouth because the lip can look deformed in a way that the front teeth can be exposed, mimicking what a rat’s mouth looks like.  It’s not the nicest name for a medical condition, especially because they are typically caused by an allergic reaction to fleas, food, or something else in the environment.

rodent ulcers on a cat
Notice the red and raw rodent ulcers on Mushroom’s lips and upper palette which are most likely painful.

The Cause

Unfortunately, Mushroom likes to chew on plastic. Many cats do, but plastic can cause an allergic reaction in some cats (and dogs). Cats can get rodent ulcers once and never again, or it can be recurrent if we can’t figure out what is causing the cat’s allergic reaction. The goal is to reduce the inflammation and discover the culprit.

The Treatment

Unfortunately, there is no test that will tell us what the best treatment for this condition is in each individual cat. Cats all have different body chemistry and therefore the treatment for eosinophilic granuloma complex is not the same in every case. It follows that some of my patients respond to certain medications better than others, so finding the right one can take a bit of trial and error. Steroids are usually the first line of therapy because they are powerful anti-inflammatories, but for some cats it just doesn’t work. Other treatments that can be effective are antibiotics or other types of anti-inflammatories.

The Outcome

Mushroom responded beautifully to a 3-week course of antibiotics, although I heard he put up quite a fuss when getting his antibiotic twice a day.

Is your cat in pain?

At Aristokatz, we love our feline patients and love solving their medical mystery. They love coming to see us because they always feel better afterward, PLUS there are no scary, barking dogs to be seen, or heard!

Contact us to see if we can help.

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