Food Allergies in Dogs

When discussing ‘food allergies’ we are really referring to a number of disorders. Some which are truly allergies, while others are non-immunologic, ‘intolerance’ reactions. These reactions can occur with anything that your pet ingests: protein, carbohydrate, or food additive. Some owners mistakenly believe that their pet can only have a reaction to a new diet. Pets can develop ‘allergies’ to the same food that they have been on their entire life. Allergies include types I (immediate hypersensitivity) and types III and IV (antigen-antibody complexes).

Clinical signs of adverse food reactions (AFR) in dogs:

Pruritis (skin itching)—can be anywhere but especially face, feet, tailhead, trunk, limbs, ears, axillae, inguinal and perineal areas

Recurrent pyoderma (skin infection)—including hot spots

Recurrent otitis externa—yeast or bacterial ear infections

Inflammatory bowel disease—frequent or excessive defecation, diarrhea, vomiting, and flatulence (gas)

Chronic otitis and pyoderma may be the only clinical signs of AFR.

Clinical signs of adverse food reactions (AFR) in cats:

Pruritus—facial lesions may or may not predominate

Miliary dermatitis—small pustules and scabs that usually start on the neck and can extend over entire body

Fur pulling—excessive grooming

Eosinophilic plaques—rodent ulcers, plaques, granulomas

Unusual (less recognized) symptoms include recurrent urticaria (hives), seizures, and vasculitis.


AFR can start at any age, but is more typically found in dogs less than 6 months of age or after 6 years of age. Any breed can be affected. It is commonly recognized in Labrador retrievers, Bichon frises, Dalmations, Sharpeis, Weimeraners, and Fox terriers.

AFR may present as a seasonal or non-seasonal dermatitis. Pets are likely to have multiple allergies—atopy (inhalent allergies), flea and food. Pruritic Threshold refers to a level of allergic stimulation necessary to produce clinical signs. This means that a dog may be both atopic and food sensitive, but may present with a seasonal dermatitis. If food sensitivities are involved, eliminating that component may place the patient below the pruritic threshold. So some patients may have their allergic symptoms controlled with restricted diets, even if they originally presented with non-seasonal allergic dermatitis.


The ONLY accurate method of diagnosing dietary hypersensitivity/intolerance involves placing the pet on a veterinary prescribed restricted elimination diet for a period of time. Some pets may show improvement in two months while others may take up to six months or longer.

Diet Selection:

After discussing your pet’s dietary history, the veterinarian will select a diet that has a ‘novel’ protein and carbohydrate source. The definition of a novel protein is a protein which the pet has never eaten! Some pets are allergic to any type of animal protein and these pets must be placed on a vegetable protein diet.

We strongly recommend that you feed your pet ONLY the diet which your veterinarian has recommended. Many people do not realize that most commercial lamb and rice diets or ‘sensitive’ diets also have small amounts of chicken, wheat, and beef, etc. These are not true restricted protein diets.

While your pet is on a hypoallergenic food trial, it is very important that your pet NOT ingest flavoured heartworm preventives, flavoured anti-inflammatory medication and antibiotics, pet vitamins, dog treats, rawhide chews, and especially NO TABLE FOOD!

You CAN give your pet carrots, apples, Royal Canin treats (these are hypoallergenic), frozen food cubes (from hypoallergenic canned food), and baked treats made from hypoallergenic dog food. To make baked treats: add water to dry food or use canned food to make patties. Bake 350F for 20-30 minutes. This will create a lingering odor!

Apply selamectin (Revolution®) on your pet as a means of heartworm prevention.

Length of diet trial:

Your pet needs to be on this special diet for EIGHT WEEKS MINIMUM! For those dogs with recurrent skin infections, we recommend continuing the diet 4-5 weeks past the normal time the pyoderma would recur after antibiotics. If no improvement is seen after eight weeks, we may recommend trying another diet (home cooked, perhaps) or intradermal skin testing for inhalent allergies.

Some patients with food allergy may have an immediate and dramatic response. In this case, we recommend continuing the special diet for several weeks past the improvement before initiating a food challenge.

Diet Challenge:

We challenge to CONFIRM and identify which ingredients our pet reacts to. Add to the restricted diet a single ingredient, each for 5-7 days with a 2-3 day period of rest in between foods. If there is no reaction, move on to the next ingredient after the rest period. Items tested: chicken, wheat, corn, dairy (cottage cheese), tuna (cats), beef, soy (tofu), eggs, other ingredients depend on previous foods (lamb, pork-pig ears), etc. Amount fed will range from 2 tablespoons to ¼ cup based upon the size of your dog. If the pet reacts, your vet will need to treat your pet (probably with steroids) to get him over the reaction completely before moving on to the next item. Most pets will react within 48-72 hours. Thirty-six percent of dogs react to one single protein. Sixty-four percent will react to multiple proteins.