My Cat Is Having Allergy Problems

Q: My husband and I are at our wits' end with a problem we are having with our 4-year-old male domestic shorthair. He is an indoor cat who started to show signs of redness, lesions and scabs primarily on the ears. Then the lesions spread to the side of his nose and chin area. He has been to two different veterinarians who both advised that is a possible food allergy. He was put on a strict diet of Hill’s Z/D dry food and canned wet food for approximately 12 weeks with very little change. He has been injected with cortisone with mild improvement as well as an injectible antibiotic and Baytril tablets for two weeks. I was also applying topical cortisone cream. He did clear for about 10 days and then the cycle started again. The vets have now suggested we take him to a feline dermatologist to start performing allergy testing to see if he has an airborne allergy. Any advice you can give would be greatly appreciated.
 
A: Although food allergy can affect the skin in a variety of ways, it typically likes to cause itching and redness around the head and face. Your veterinarian is correct to put food allergy at the top of the list. The way you prove that it is food allergy is to feed a strict hypoallergenic diet and see if the clinical signs resolve.This can take anywhere from three to 12 weeks. You were feeding the most hypoallergenic diet out there (Hill’s Z/D), for a full 12 weeks with no improvement. I think we can safely say that food allergy is not the culprit. The fact that there was some improvement with a steroid (cortisone) injection suggests that this might be atopy (inhalant allergies) or perhaps an autoimmune disease. Cortisone injections wear off after a short period of time, and your cat’s signs probably returned because the steroid wore off. 

In looking at the photos you sent, I notice that your cat’s ear tips are crusty. This is very suggestive of an autoimmune skin disorder. Sometimes, for reasons unknown, the immune system will make antibodies against components of its own skin. That’s what this looks like to me. In particular, I think it looks like the autoimmune disease called pemphigus foliaceus. 

The way you make a definitive diagnosis is by biopsy. Have your veterinarian obtain a biopsy sample of an affected area of skin. Cats have a small flap of skin behind each ear that seems to serve no real purpose. If these flaps are affected (they sometimes are), ask your vet to obtain his sample from these flaps. You’ll get a diagnosis and it will still look cosmetic. If the flaps are not affected, he’ll have to take a small piece of the affected skin, which is no big deal. It is important to get a proper diagnosis. If it is pemphigus foliaceus, it is treatable with immunosuppressive drugs. Most cats respond readily, and do well in the long term.