Q: My 3-year-old cat has a persistent sore on her upper back. We have taken her to the vet three times now. She was treated with antibiotics and cortisone shots as well as flea treatment. The sore persists although it is now dry and scabbed over. Can we do anything else for her? The vet did not know what could cause this; maybe a food allergy although she has not been given any new foods.
A: Many cats with skin allergies will develop a large circular red sore on their back, often right in the middle of their back in the shoulder blade area. Often, the sore will ooze a little serum, and it can sometimes become infected. These are similar to “hot spots” that commonly develop in dogs. A few things can cause them.
Inflammatory or Auto-Immune Condition Anti-inflammatory medication — steroids such as prednisolone, a synthetic version of cortisone — often cause the sore to resolve. I personally prefer to prescribe tablets rather a steroid injection, as I feel it is safer. Steroids didn’t work, so an inflammatory or an auto-immune condition seems unlikely.
Bacterial Infection If a secondary bacterial infection develops, it might need antibiotics. Antibiotics didn’t work, so an infection is unlikely.
Flea Allergy Cat flea allergy can certainly cause scabs throughout your cat’s skin, but usually doesn’t cause a persistent open sore. Flea treatment didn’t help, so fleas are unlikely to be the cause.
Food Allergy Cat food allergy can present in a variety of ways, although a persistent sore is not your typical presentation. I’m surprised that the steroid injections had no effect. The next step is to determine whether your cat has a food allergy.
How to Determine Whether Your Cat Has Food Allergies
• Start a hypoallergenic diet. A hypoallergenic diet contains a protein source that your cat has not been exposed to before, such as rabbit, venison or duck. (Most veterinarians carry prescription diets designed for this purpose.)
• Feed this food, and ONLY this diet, for up to 10 weeks, before concluding whether or not food allergy is the culprit.
• Alternatively, you may opt for a skin biopsy. This simple procedure will very likely reveal the diagnosis.
Considering the number of treatments that you’ve tried with no success, I think you need a biopsy at this point. Another option would be to consult with a board-certified veterinary dermatologist. Your veterinarian can direct you to an appropriate referral center.