OT:Food Allergies: The Truth About Lamb and Rice Mixes
By Sarah Probst
Information Specialist
University of Illinois
College of Veterinary Medicine
cvm.uiuc.edu
"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 causes.
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.
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