Food Allergies in Cats

Food allergies affect about 10 percent of American pet cats. Although these allergies seem to develop overnight, they are actually the result of your cat eating the same food for a period of time. If she's allergic, her body will reach a point at which it begins to create a defense against whatever ingredient in the food her body perceives as a threat.

How a Food Allergy Develops

Your cat's food allergy is a result of her immune system overreacting to a trigger called an allergen. When her immune system reacts to the histamine, it produces a chemical called histamine that causes inflammation and itchiness in her skin. Histamine can cause hives to rise on your cat's skin. Most feline food allergies show themselves between the ages of two and six years, although food allergies can and do develop at any time in a cat's life.

Beef, dairy products and wheat are the top three causes of feline food allergies. Other common pet food ingredients that have been identified as allergy triggers include:

  • Cereal grains
  • Chicken
  • Fish
  • Soy

Symptoms of a Feline Food Allergy

Here are some of the symptoms that may indicate that your cat has a food allergy:

  • Excessive licking and scratching
  • Hair loss, especially around the head and neck
  • Irritated skin
  • Itchiness that doesn't go away after topical steroid treatment
  • Miliary dermatitis (red, crusty skin bumps)
  • Recurring ear infections that resist treatment
  • Smelly skin

The symptoms of a feline food allergy resemble a number of other common feline allergies, which is why your veterinarian will need to conduct diagnostic tests to determine the exact cause of her allergies.

Feeding an Exclusion Diet

One of the most common tests for a pet's food allergy is to feed the animal an exclusion diet for about 12 weeks. This diet features a novel source of both protein and carbohydrate that your cat has never eaten before. Novel protein and carbohydrate combinations include duck and green pea, lamb and rice, or turkey and potatoes. As she eats this diet for the trial period, her symptoms should clear up.

No other foods, supplements or flavored treats or medications should be given during the trial period - just the exclusion diet and water. Adding other foods to the exclusion diet will delay a diagnosis and could make your cat's symptoms worse, neither of which are helping to solve her problem.

At the end of the trial, your veterinarian will likely test your cat by reintroducing ingredients from her former diet. When her symptoms reappear, the diagnosis of food allergy is confirmed. After the allergy tests are complete, many cat owners choose to feed their pets the exclusion diet as the cat's new regular diet.

A newer approach to allergy testing involves the use of special diets called limited antigen diets. These diets are also called hydrolyzed protein diets, and the proteins and carbohydrates in them have been specially treated to be too small to cause your cat to have an allergic reaction. These diets can also become a cat's regular diet after testing has been completed.