What Are Cats Allergic To?

By Lorie Huston, DVM on May 21, 2012

It’s that time of year again. Spring-time heading into summer. The fleas are out in full force. Plants are blooming. Pollen is flying. And your cat may be suffering from allergies.

In cats, allergies most commonly surface as skin problems rather than respiratory problems like they do in people. We do occasionally see respiratory symptoms due to allergies, but generally cats suffering from allergies are itchy. They may have bald spots and/or sores and scabs on their skin.

What are cats allergic to?

There are a few different things cats can be allergic to, and fleas top the list. Commonly known as flea allergy dermatitis, or FAD, flea allergies are extremely uncomfortable for your cat. And not seeing fleas on your cat doesn’t rule out the possibility of a flea allergy causing your cat’s skin problem either. Cats groom themselves constantly - even more so when they have allergies. Through grooming they may remove the evidence of a mild flea infestation. Plus it only takes one flea bite to set off the allergy. Just one.

Atopy is another common allergy we see in cats. Atopy is an allergy to something your cat is in contact with in his environment.

Food allergies can occur as well. Your cat can actually become allergic to an ingredient or ingredients in his diet.

How are allergies in cats best treated?

The best treatment depends on the cause of the allergy. Flea allergies are treated by eliminating the flea population. Atopy is treated by avoidance (if possible) and sometimes with other anti-inflammatory medications or "allergy shots," which hyposensitize the cat to the substances to which he is allergic. Food allergies are treated by avoiding the food ingredient that is causing the allergy.

Unfortunately, one of the problems encountered with skin allergies is that all of these allergies look exactly the same. It’s impossible to simply look at a cat and say, "That cat has a food allergy," and "That one has atopy." There are clues that can give hints as to the cause. Finding flea dirt or living fleas on a cat means that a flea infestation is present and must be treated, obviously. Skin problems that are seasonal are more likely to be atopy, or possibly flea allergies. Food allergies most often cause symptoms year round. But even these rules are not set in stone and an individual cat can suffer from more than one type of allergy as well. Some cats suffer from both flea allergies and atopy at the same time, for instance.

As a result, treatment of a skin problem often involves a multi-faceted approach. Effective flea control is almost always advisable to rule out the possibility of a flea allergy. A special diet may be recommended as a feeding trial in case of food allergies. Use of medications such as corticosteroids and cyclosporine (Atopica) are controversial but they are used by some veterinarians. Secondary skin infections may require antibiotics. (Secondary skin infections are common for cats that have allergies and are a result of the trauma to the skin caused when your cat scratches.)

Consult your veterinarian to determine the best course of action for your cat if you think your cat has allergies. Your veterinarian can help you diagnose your cat’s problem and can help you to choose a flea product that is safe and effective for your cat, a food that is suitable, and to determine what other medications, if any, may be needed.