Food Allergies in Dogs

By Ryan Llera, BSc, DVM; Catherine Barnette, DVM; Ernest Ward, DVM

What is a food allergy?

A food allergy is one of the most common allergies or hypersensitivities known to affect dogs. In a pet with an allergy, the immune system overreacts and produces antibodies to substances that it would normally tolerate. In an allergic reaction to a food, antibodies are produced against some part of the food, usually a protein or complex carbohydrate. Since antibody production is required for an allergy to develop, food allergies usually manifest after prolonged exposure to one brand, type, or form of food.

What are the clinical signs of food allergies in dogs?

In the dog, the signs of a food allergy are usually itchy skin, paws, or ears or digestive disturbances such as vomiting or diarrhea. Other more subtle changes can also occur, including hyperactivity, weight loss, lack of energy, and even aggression.

Are some ingredients more likely to cause allergies than others?

The most common food allergens in dogs are proteins, especially those from dairy, beef, chicken, chicken eggs, soy, or wheat gluten. Each time a pet eats food containing these substances, the antibodies react with the antigens, and symptoms occur. Virtually any food ingredient can produce an allergy, however. Proteins are the most common culprits but other substances and additives can also be responsible.

How is a food allergy diagnosed?

The best and most accurate method of diagnosing a food allergy is to feed a hypoallergenic diet for 8 to 12 weeks as a food trial, called an elimination trial. To be a true elimination trial, this special diet must not contain any ingredients that your dog has eaten in the past. It also requires that no other foods, treats, or supplements are fed during the trial period, including flavored vitamins and certain parasite preventives.

If your dog's allergy symptoms resolve while on the food trial, the next step is to perform a food challenge by re-introducing your dog's old food. If your dog's symptoms resolve with the food trial and return within one week of a food challenge, your dog has been definitively diagnosed with a food allergy.

How is a food allergy treated?

Once the offending food substance has been identified, a diet that does not contain it is chosen. Today, there are several hypoallergenic diets available from your veterinarian that can be fed for the rest of your dog's life. There are three types of hypoallergenic diets:

  • Veterinary hydrolyzed protein diet, in which the protein molecules are broken down to a size too small to be recognized by your dog’s immune system (e.g., Hill's Prescription Diet z/d®, Royal Canin Hypoallergenic Hydrolyzed Protein® or Anallergenic™, and Purina ProPlan Veterinary Diets HA Hydrolyzed®).
  • Veterinary novel protein diet that does not contain any products that were present in your dog’s previous foods (e.g., Hill's Prescription Diet d/d®, Royal Canin Selected Protein PD® or Selected Protein RC®, Rayne Nutrition Kangaroo-MAINT™, Rabbit-MAINT™, or Crocodilia-MAINT™)
  • Home-prepared novel protein diet that does not contain any ingredients that were present in your dog’s previous diets (must be formulated by a veterinary nutritionist and typically requires the addition of a balancing supplement such as Hilary’s Blend for Dogs™ or Balance IT®).

Some dog foods available in retail stores may tout that they are "limited-ingredient" or do not contain the ingredient(s) that your dog is allergic to, but it is important to note that, unlike veterinary diets, retail pet foods are not manufactured with the extreme health and safety protocols to prevent cross-contamination.

Your veterinarian will prescribe the best option specific to your dog’s needs.

Can food allergies be cured?

There is no cure for food allergies in dogs. The only treatment is avoidance. Some dogs will require medication during severe episodes, but most pets can be successfully treated with a hypoallergenic diet.

Is it likely that my dog will develop other food allergies?

Dogs that have developed an allergy to a particular food may develop other food-related allergies in the future. In addition, many dogs with food allergies have other allergies, such as atopy (inhalant or environmental allergy) or a flea allergy. If you think your pet may have a food allergy, you should discuss this with your veterinarian, who can help your pet resume a healthier, more comfortable life.

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