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Food Allergies: The Truth About Lamb and RiceMixes

Pet Column for the week of July 6, 1998

Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
By Sarah Probst
Information Specialist

"Some food allergy cases have symptoms of gastrointestinal upset-diarrhea, vomiting or
increased bowel movements per day--but in many cases, the only sign is itching," explains
Dr. Kinga Gortel, veterinarian and resident at the University of Illinois College of Veterinary
Medicine Teaching Hospital. When your pet itches excessively, there may be a variety of

In humans, food allergies can be diagnosed via skin tests and blood tests, but unfortunately,
these tests are unreliable in pets. "Veterinarians prefer to do a restrictive diet trial," says Dr.
Gortel. "This consists of taking away your pet's normal diet-including treats, chewables, and
flavored vitamins-and switching your pet to a diet containing proteins and carbohydrates
completely novel to your pet." When possible, Dr. Gortel has the owners home-cook for
their pet during the diagnosis period. "Then we know for sure that the diet doesn't have
additives or preservatives and hasn't gone through a feedmill or processing plant that might
contaminate food with proteins your pet has been exposed to. It doesn't take much to set
your pet off if he is allergic to something."

It is also important that owners make sure that their dog or cat remains inside to prevent
hunting of wildlife or foraging for garbage. "For dogs, it is also good to eliminate exposure
to cat food, or cat litter--some dogs find cat feces to be tasty morsels," adds Dr. Gortel.

"Veterinarians used to recommend lamb and rice a lot for restrictive food trials because it
was a food source not found in normal mixes. Lamb and rice was recommended for food
allergy testing for so many years that the public got the impression that it was good for the
skin. Companies started advertising their lamb and rice mixes as 'recommended by
dermatologists.' So now if you go to a pet store, you can find a fairly wide selection of lamb
and rice foods, most of which also contain corn, beef, chicken, and other components.
These lamb and rice mixes do provide a complete diet; however, a lamb and rice diet is not
inherently better than a normal diet. The popularity of the mixes has made them undesirable
for restrictive diet trials unless owners know that their pet has never eaten a lamb and rice
mix and unless there are no other protein or carbohydrate sources in the lamb and rice mix,"
clarifies Dr. Gortel.

Now, veterinarians must turn to more exotic sources of protein such as fish, rabbit, or
venison, and carbohydrates such as potatoes or yams. Sometimes Dr. Gortel will
recommend a vegetarian diet. "The home-cooked meal is not usually very balanced, so we
only feed it for about two or three months. But if pets have a food allergy, this is long
enough for a diagnosis." The veterinarian will first have owners wean pets from their normal
diet and start the elimination diet with an overlap of four days-feeding both diets at the same
time. Once the home-cooked diet is fed exclusively, pets are monitored for improvement. If
in 8 to 10 weeks your pet has not shown any improvement at all, then itching is probably
not caused by a food allergen.

If your pet does improve on the home-cooked diet, then veterinarians re-challenge your
pet's system by reintroducing the original diet. When food trials are initiated, veterinarians
may prescribe a new shampoo, antibiotics, and anti-inflammatories. Reintroduction of the
original diet will let veterinarians know if the new diet or if prescriptions caused
improvement. Reintroduction takes 5 to 7 days. If your pet does not get worse during
reintroduction, a food in the original diet did not cause itching. The itching may be from an
environmental or parasitic source. Skin tests may need to be done. If itching does resume
during reintroduction, the food trial test is continued to determine which food component
causes allergic reaction in your pet.

"Veterinarians then go back to the ingredient list on the original diet and check through the
ingredients, exposing the animal to them with the home-cooked diet," explains Dr. Gortel.
After harmful ingredients are pinpointed, veterinarians can recommend a diet that does not
contain those ingredients. Many commercial diets are available which fulfill your pet's needs.

"When owners try to do food trials themselves, the diagnosis becomes more difficult,"
explains Dr. Gortel. When your pet is itching, switching them randomly from food to food
exposes your pet to a number of protein sources. This makes it hard for veterinarians to
find a new protein source to suggest for home-cooking. "Sometimes owners find food trials
tedious or they cannot stand the fact that their pet cannot have a treat. They quit halfway
and then the veterinarians' dilemma is how to convince clients to do the trial again for the
pet's sake."

Food allergies probably have manifestations in your pet which we cannot see. In humans,
food allergies are associated with behavioral and emotional manifestations. "Dogs may be
feeling extremely lousy in addition to being itchy. Some dogs with food allergies have been
known to have seizures," explains Dr. Gortel.

"Veterinarians and researchers still debate what causes food allergies. One theory is that
exposure to intestinal parasites might predispose your pet to developing a food allergy.
Exact mechanisms of the reaction remain undefined. If we knew exactly why pets get food
allergies, we could avoid them; unfortunately, it is a complicated disease. However, once
you eliminate the food causing the problem, your pet becomes much more comfortable."

If your dog experiences extreme itching with or without gastrointestinal problems, contact
your local veterinarian.