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Veterinary Medicine
Instructions for Veterinary Clients

Food Hypersensitivity
(Food Allergy)
From Duclos: Canine and Feline Skin Diseases

General Information

An allergy is a condition in which the body reacts adversely to substances such as pollens, dusts, molds, insects, mites, fibers, or foods. The substances that the body reacts to are called allergens. Allergy symptoms in dogs and cats include scratching, rubbing, biting, and chewing the skin. Allergies develop after continued exposure to allergens in pets that have inherited the allergic trait from their parents. A food allergy is usually caused by eating the offending food substance for months to years. Pets do not become allergic to a brand name (e.g., Purina, Alpo); they become allergic to specific ingredients in the diet. The most common food allergens reflect the most common diet proteins found in pet foods. In the United States, these include chicken, beef, soy, corn, milk, eggs, wheat, fish (cats only), and more recently, lamb. Reaction to lamb is not a common finding, however.

To make a food allergy diagnosis, the animal has to be fed a diet that eliminates any food proteins the animal is presently eating. This is called an elimination diet. For example, if your pet is not eating any lamb protein, a diet of lamb with a carbohydrate such as rice or potato will eliminate all the other meat proteins. The majority of the so-called lamb and rice diets in the United States today contain not only lamb but also many of the other common food proteins (chicken, beef, soybean, corn, milk, egg, and wheat). Thus most of the so-called lamb and rice diets do not qualify as elimination diets. The process called food elimination involves a diet that eliminates all previous food proteins. Other food allergy tests, such as skin testing or a blood test, are not reliable.

Important Points in Treatment

  1. The best control for allergy is avoidance of the allergenic substances.
  2. Finding what substance is causing the reaction in the food allows you to avoid feeding it to your pet.
  3. A strict food elimination diet must be followed for 9 weeks in dogs and 10 weeks in cats; most allergic pets will show some improvement within 3 weeks.
  4. If a pet shows improvement on a food elimination diet, you must prove that it is a food allergy by seeing a repeat of signs on the previous diet.
  5. Testing individual ingredients will show which substance causes the allergic signs.

Treatment Instructions

Notify the Doctor if Any of the Following Occur

  • The signs worsen or new signs appear.
  • Your pet will not eat the prescribed food.
  • Your pet has diarrhea or vomiting.

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