Cat's Sore Could Be Food Allergy

Cats can get "hot spots" like dogs. Our veterinary expert explains what causes cat skin outbreaks.

By Arnold Plotnick, DVM | Posted: August 23, 2012, 4 p.m. EST

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Cat With Food Allergy at Dish
A food allergy can cause a skin outbreak in cats.
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.
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Reader Comments

Angie    Windsor Mill, MD

6/10/2015 6:56:56 PM

Good article. Good advice. In February, my 3 year old Aby suddenly developed a round, raw wound on his right neck. The vet believed it was related to a problem with his teeth. So I paid the $600 for dental work. But a couple weeks later, the wound returned. This time I immediately knew the culprit - his food. I've always fed my cats Wellness Cubed Chicken Entree. But this year, the store has sometimes been out of the food. My last trip to purchase cat food, I'd bought Wellness Minced Chicken Entree. The same thing had happened in February. I returned unused cans of Wellness Minced Chicken Entree and will never purchase it again. I have no idea why the Minced version is a problem. Recently, I've switched to feeding my cats more of a raw diet. I feed either Primal Freeze Dried Turkey or the Freeze Dried Chicken with Salmon foods mixed with a little of the Wellness Cubed Chicken Entree. The Aby hasn't had any further problem and both of my cats have very healthy looking coats. Surprisingly better than when they ate only the Wellness Cubed.

Eva    Seattle, WA

5/19/2015 9:03:06 AM

I have a 9 year old black cat, she used be pretty overweight when I adopted her. Then we have slimmed her down, she also has since summer is here basically. She has started to aggressively groom herself so much that she's biting herself and creating sores. She has a pretty great routine everyday and is indoor/outdoor. The only thing I can think of is allergies. We have changed her food, but it has not really helped. We have also given her calming pills. She has lived in the same place and eaten the same food since we rescued her. I just don't see what she could be allergic to if everything is the same.

charlene    Poughkeepsie new york, NY

3/11/2015 4:31:24 AM

I adopted a kitten 7months old she is adjusting well
,went to vet.I noticed her fur looked almost 2toned so I was able to get a closer look and found fur missing and an old soar about an inch long with scabs on it there is no bleeding,or oozing but it never got detected when she released to me or the vet what should i do.

PounceandPlay    Portland, OR

3/4/2015 4:19:15 PM

Thanks for the heads up! If I notice any skin problems or sores, I'll keep this in mind.

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