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Food Allergies in Cats

By Catherine Barnette, DVM

Medical Conditions, Pet Services

What is a food allergy?

The term food allergy is used to describe an abnormal immune-mediated reaction to an antigen within food. In other words, food allergy refers to a reaction caused by the immune system (an allergic reaction) to a specific protein found within food.

Although we understand the mechanism by which food allergies occur, it is not known why these allergies occur. We do not understand why some cats develop food allergies and others do not.

What foods are associated with food allergies?

In order for a cat to develop a food allergy, the food must be one to which the cat has been previously exposed. An animal cannot develop an allergy to a food that it has not been exposed to.

The foods most commonly associated with food allergies in cats include beef, fish, chicken, and dairy products. Limited research has been performed in this area, and there may be other common allergens that we have not yet identified.

What are the risk factors for food allergies in cats? cat_scratching_2

Food allergies can develop at any time during a cat's life.

Genetic predisposition plays an important role in food allergies. Food allergies are also often related with atopy (inhalants allergies) – many cats are allergic to both food ingredients and environmental allergens. See handout “Inhalant Allergies (Atopy) in Cats” for further information on atopy.

"Food allergies are also often related with atopy."

Male and female cats are both equally likely to develop food allergies.

What are the signs of food allergies?

Cats with allergies often present with chronic, year-round itching and skin inflammation. This itching typically affects the face, ears, belly, groin, armpits, and the legs/paws. These cats are so itchy that they often over-groom themselves, causing significant trauma (wounds, abrasions) and hair loss.

Affected cats may also develop recurrent infections of both the skin and ears. In some cats, these infections may be the only clinical sign of food allergies. 

In some cases, cats with food allergies develop gastrointestinal signs, such as vomiting or diarrhea, in addition to their skin issues. These cats may develop itching around the rectum, which leads to scooting. Cats with food allergies may also have frequent bowel movements, or strain when they are defecating.

How will my veterinarian diagnose food allergies?cat_food

The chronic itching associated with food allergies can also be caused by a number of other conditions, such as mites, bacterial infection, yeast infection, or other allergies. Therefore, testing is required in order to determine the cause of your cat's skin condition.

The most reliable test for diagnosing food allergies is a food trial. This test involves feeding a special diet, one which does not contain any proteins that your cat has been previously exposed to, for 6-8 weeks. A food trial diet may take a number of forms:

  • a hydrolyzed-protein diet (one in which the proteins are broken down to a size that is too small to be recognized by your cat's immune system),
  • a commercially-available novel protein diet (one that does not contain any products that were present in your cat's previous foods), or
  • a home-cooked novel protein diet (also one that does not contain any products that were present in your cat's previous foods).

Your veterinarian will help you determine the best option for your cat.

While your cat is on a food trial, she must eat ONLY the food that has been recommended by your veterinarian. It is very important that no other treats, supplements, or other edible products be fed during the food trial. Be vigilant about cleaning dishes off the table after your family meals, because even licking a plate clean may interfere with the results of a food trial. Your cat can only receive the prescription food, water, and unflavored prescribed medications (which cannot be disguised using food) during a food trial.

"If your cat's signs resolve with the food trial AND return within one week of a food challenge, your cat has been definitively diagnosed with a food allergy."

If your cat's allergy symptoms resolve while on the food trial, the next step is to perform a food challenge. This involves re-introducing your cat's old food.

If your cat's signs resolve with the food trial AND return within one week of a food challenge, your cat has been definitively diagnosed with a food allergy.

How are food allergies treated?

Food allergies, like other allergies, cannot be cured. Instead, they are managed through avoidance of foods that trigger allergy flare-ups.

Once your pet has been diagnosed with a food allergy, you may choose to continue the food that you used during the food trial for long term maintenance. Alternatively, you may be able to work with your veterinarian to find a different food that will provide similar relief from symptoms. Every cat differs in the severity of their food allergies. Some cats may react dramatically to even trace levels of an offending allergen, requiring carefully controlled hypoallergenic foods, while other cats may have a higher tolerance and may do well on a different ‘flavor’ of a typical cat food.

"Food allergies, like other allergies, cannot be cured."

Regardless, once you have found a diet that works for your cat, you will need to continue that diet long-term, avoiding cat treats and other foods that may trigger an allergic reaction.

With careful dietary control, the prognosis for cats with food allergies is typically good.

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