FOOD ALLERGY

About the Diagnosis

Cause: A food allergy is a reaction by the immune system to particular foods or food ingredients. For unknown reasons, in a small number of dogs and cats the immune system mounts an unusually strong response to some foods. The most common causes for both dogs and cats are proteins found in beef, chicken, dairy products, eggs, wheat, corn, and soy. In cats, fish is also included in the list. Some breeds appear to be predisposed to developing food allergies. It is important to understand that food allergies develop only after the immune system has been previously "exposed" to a food. In fact, most dogs and cats have been eating a particular food for months or years before adverse reactions like allergies to it are noticed.

Food allergies can develop in dogs and cats ranging in age from several months to their geriatric years. Symptoms include itchiness (pruritus), dry or crusty skin, and hair loss (alopecia); one or more parts of the body can be affected. These include the ears, face, paws, the area around the anus, armpits, and groin, and others. Secondary infections (bacterial, yeast) of the skin can develop, and self-induced trauma of the skin can be a problem. Intestinal disturbances including frequent bowel movements, loose stools, diarrhea, or vomiting occur in some cases. Food allergies cause skin-related symptoms similar to those seen with several other allergies such as flea and inhalant (atopy) allergies.

Diagnosis: Your veterinarian will perform a thorough physical exam and take a complete medical/dietary history. Be sure to list everything that is ingested-food, treats, heartworm medication, hairball treatment, feces (coprophagia), etc. It doesn't matter if it has been consumed for years or weeks-include everything. To diagnose this disorder, the suspected food is completely eliminated from the diet for approximately 4 to 12 weeks. During this time, your veterinarian will provide a commercially-prepared diet that is nutritionally complete. Home-prepared diets are another option. It is essential to consult with your veterinarian in order to ensure that any home-made diets contain all nutrients, to avoid serious health problems related to nutritional deficits. Your veterinarian will discuss diet options with you. It is important that your dog or cat has never had any ingredient in the diet before and that this is the only food offered during this trial period. If your dog or cat improves while on this diet, then a food allergy is very likely the cause of the symptoms. At this time, they are "challenged" with the food that was eliminated, to be sure improvement was not just the natural course of some other skin or intestinal disorder. If symptoms worsen or return, then that food is the probable cause and it must never be fed again, so as to avoid recurrent symptoms.

Living with the Diagnosis

Avoid giving the allergenic food altogether. Even a small amount can cause full-blown symptoms in some dogs and cats. You may need to read ingredient labels carefully before buying food and treats. All family members need to observe this rule, and if your pet is kenneled, be sure that the kennel employees are informed. If you have more than one dog or cat in the household, adherence may require changing the diet for all to prevent the possibility of consuming the others' food.

Give all medications as directed and know the possible side effects.

Treatment

Antihistamines or corticosteroids may be given to control itching. Antibiotics or other medications help to control secondary infections. Special shampoos may make your dog or cat more comfortable. These are temporary solutions, and tackling the root cause of the allergy is the best way of eliminating symptoms. When the allergenic food or food ingredient is identified, it is strictly avoided.

Rarely, severe reactions to food (anaphylaxis) occur. Hives, facial swelling, and/or breathing problems result. This can be an emergency; take your pet to your veterinarian or to the local veterinary emergency clinic immediately.

DOs

• Provide a thorough list of all things that your dog or cat eats.

• Inform your veterinarian if your dog or cat has ever been diagnosed with a medical condition and is taking medication.

• Realize that even one exposure (one bite) of a food or treat that is allergenic can cause days or weeks of symptoms, and that strict adherence to a hypoallergenic diet is essential in pets with food allergy.

• Give medication exactly as directed by your veterinarian, and if you are concerned about possible negative effects, discuss them with your veterinarian immediately rather than simply discontinuing the treatment.

DON'Ts

• Do not give any other foods (including treats, chewable medications like heartworm preventative flavor cubes, etc.) than the one selected by your veterinarian after the food trial has started.

• Do not give medication that you have at home that has been prescribed for human use; some of these may interfere with treatment and cause even more severe problems.

When to Call Your Veterinarian

• If your dog or cat will not eat the trial diet-cats that don't eat can develop serious complications.
• If you cannot keep a scheduled appointment.
• If you are unable to give medication as directed.

Signs to Watch For

• Watch for general signs of illness, which include vomiting, diarrhea, decreased appetite, weight changes, and changes in behavior such as hiding more than usual and aggressiveness.

• Watch for signs of food allergies, which include itching, redness, crusts or scales on the skin, frequent bowel movements, loose stools, vomiting, and diarrhea.

Routine Follow-Up

• Follow-up appointments are scheduled during the food trial and subsequent challenge to monitor progress.

Additional Information

• Although one food or food ingredient may be identified as an allergen, allergies to other foods can develop later in life. See your veterinarian if symptoms return.