Cat Food Allergy Diagnosis

Cases of cat food allergy accounts for more than 50 percent of all itching and scratching in cats. It is the third most common allergy in cats after flea allergy and inhalant allergy.

Food allergies are most often caused when a cat's digestive system becomes sensitized to one or more ingredients in his diet. The cat's body fights the sensitivity by creating histamines, which cause the outward clinical signs. Diagnosing the problem takes time and patience from the owner to restore the cat's health.

Clinical Signs of Feline Food Allergy

Clinical signs of food allergy in cats include:

  • Dull coat
  • Excessive scratching or bitingHair loss
  • Persistent scratching around the head and neck
  • Red, irritated skin

Diagnosing a Feline Food Allergy

According to the Merck Veterinary Manual, "There is no reliable diagnostic test other than a strict food elimination diet." Laboratory tests are ineffective in diagnosing feline food allergy and medications provide only short-term relief from the itching and scratching. Changing diets without conducting the food elimination test doesn't solve the problem, either, because many commercial diets contain similar ingredients.

Since the main clinical sign of food allergy is itching, the best was to confirm the diagnosis is to place the cat on a hypoallergenic diet, then look for a decrease in itching. It generally takes about three months of feeding the hypoallergenic diet before a diagnosis can be made. The hypoallergenic diet must not be supplemented with treats or other foods because additional ingredients may cause allergic reactions in your cat, prolonging the diagnosis. Food elimination diets can be challenging for cat owners because their pets can be reluctant to try new diets.

The most common food allergens in cats include fish, beef and chicken. The hypoallergenic diet will contain new sources of proteins and carbohydrates that your cat has never eaten. New protein sources may include pork, venison, lamb or rabbit. He will eat only the hypoallergenic diet as recommended to give your veterinarian a chance to evaluate his reaction to the diet. If your cat shows no clinical signs of itching or scratching after he's completed the hypoallergenic diet trial, you may be asked to feed your cat his original diet to determine if a food allergy is the cause. If your cat begins itching and scratching after he resumes eating his old diet, a food allergy is the likely culprit. If your cat doesn't respond to the hypoallergenic diet, your veterinarian may repeat the three-month test with a different hypoallergenic diet.

In some cases, a hydrolyzed protein diet may be recommended. This relatively new type of diet contains proteins and carbohydrates that are specially formulated not to cause an allergic reaction.

Treating a Feline Food Allergy

Once the allergy-causing ingredient has been identified in your cat's diet, it must be eliminated. This usually means changing your cat's diet to a new protein source that does not cause your pet to itch and scratch. In time, some cats may re-develop clinical signs of food allergy if the new protein source causes an allergic reaction, but most are able to thrive on their new hypoallergenic diet.