Food Allergies in Dogs

Just like people, your dog can get allergies, too. Although it’s not too common, allergies can be the result of your dog’s food. But oddly enough, allergies do not spring up because of a new food introduced in your dog’s diet; usually they involve the food your dog has been eating for years.

Food allergy is an uncommon problem in dogs and it can start at any age. A change in diet is not necessary for development of food allergy. Most affected pets (70 percent) develop allergies to food ingredients that they have been fed for a long time, usually more than two years. In fact, if your dog has an immediate adverse reaction to a new food, it is probably not an allergic reaction, because it takes more than one exposure to produce an allergic reaction. Food ingredients most commonly responsible for allergies are beef, chicken, fish, eggs and milk. The tendency to develop allergies is genetically determined. Dogs with other allergies (inhalant allergies or atopy) may be at increased risk for developing a food allergy.

The clinical symptoms of food allergy resemble those of other types of allergies (inhalant allergies or atopy). These two disorders may have the same clinical symptoms and the same distribution of itchiness (pruritus) over the dog’s body. In some cases, it is impossible to differentiate between inhalant allergy (atopy) and food allergy by clinical appearance alone.

Food allergy should be ruled out first because it is the easier of the two disorders to control by eliminating the offending food ingredient from the dog’s diet. Food allergy is ruled out by feeding a diet consisting solely of food ingredients to which the animal has not been previously exposed, an “elimination food trial.” This trial should be performed before considering expensive tests (skin testing) for other types of allergies.

What to Watch for

Signs of food allergies in dogs may include:

• Itchy (pruritic) skin, especially around the face, paws and ears
• Bad skin odor, excessive scaling, red bumps (papules) and ear infections, may be observed in dogs with chronic food allergy
• Self-inflicted skin trauma resulting from severe itching
• Diarrhea and vomiting, although most dogs with food allergy only develop skin problems.

Diagnosis of Food Allergies in Dogs

Diagnostic tests are needed to recognize food allergy and exclude other diseases that may cause similar symptoms. Tests may include:

• A complete medical history and physical examination. Your veterinarian will examine the skin closely and inquire about your dog’s dietary history. However, most animals that develop food allergy have not had a recent change in diet and have been eating the same food for a long period of time.
• An “elimination food trial.” This test consists of identifying a diet that contains ingredients to which the pet has never been exposed (novel source of protein and carbohydrate) and strict feeding of this food alone for 8 to 12 weeks. Food allergy is considered a possibility if the itchiness and scratching subside and your dog does not develop relapsing skin or ear infections during the food trial.

Treatment of Food Allergies in Dogs

Treatment for food allergy in dogs may include one or more of the following:

• Avoidance of the offending food or food ingredient
• Antihistamines (Benadryl) to decrease the itching
• Treatment of secondary bacterial or yeast infections

Home Care

New food allergies can develop over time. If your dog previously was diagnosed with food allergy and has been well controlled with a special diet but once again is showing signs of allergic skin disease, your dog may have developed a new allergy. Under these circumstances, consult your veterinarian to determine whether a new allergy has developed, or whether another disease is present.

Another “elimination food trial” may be necessary to make this distinction. Patience and determination are very important for the success of an “elimination food trial.” You and your family must be strict and be certain that no one “breaks” the food trial by giving the dog treats or table scraps. Strict compliance with the trial is essential for proper interpretation of the results. This means no treats (milk bones, rawhide bones, pig ears), flavored medications (Heartgard Plus), or flavored vitamins during the trial.

Preventative Care

A genetic predisposition seems to exist for food allergy. Based on their genetic constitution, some animals seem to be predisposed to development of food allergy. However, since the cause of food allergy is unknown, the disorder cannot be prevented.