Food sensitivities and allergies are increasing problems. Many pet owners have animals tested to determine which ingredients cause allergic reactions. Once the laboratory report comes back, they then seek a food that does not contain the incriminated ingredient. Manufacturers cheerfully respond with new varieties of supposedly hypoallergenic foods.
The results of such an approach, however, are disappointing. The reason is that pet foods are not made up of singular ingredients. They are also not made up of the same things that laboratories use to test for allergies.
Pet foods can be comprised of as many as fifty different ingredients, all processed under rigorous conditions, including high temperature and hundreds of pounds per square inch of pressure. With such food "torture," the molecular makeup of the food changes. The starting materials are transformed into different ingredients. Fifty starting ingredients transform into hundreds of food fractions and chemical novelties.
Allergy testing laboratories use protein isolates. This is not the same as the end product of processing. Beef, chicken, corn and soy in a pet food are not the "beef," "chicken," "corn" or "soy" used in a laboratory.
Consider this quote from a recent study regarding allergies: "…Diagnosis requires dietary elimination-challenge trials and cannot be made on the basis of clinical signs, routine clinicopathological data, serum antigen-specific IgE assay, gastroscope food sensitivity testing or gastrointestinal biopsy…" Guliford, W. Grant, et al. Food Sensitivity in Cats with Chronic Idopathic Gatrointestinal Problems. Journal of Veterinary Internal Medicine, 15 (1), 7-13, 2008. In other words, there is no way to determine the tolerance to a food by merely evaluating an ingredient label.
Therefore, the only way to test an animal for sensitivity or allergy to a commercial pet food is to actually feed the food over a period of time to observe results.*
Attempting to treat allergies by removing an allergen - usually impossible to do - solves only part of the problem. Focus needs to be redirected to feeding foods which will enhance immune system health and prevent allergic reaction. Additionally, no food should be fed day in and day out. Variety is not only key to nutrition but also to prevention of toxicity and allergy (see Myth of the 100% Complete Pet Food).
* Wysong Health Letter, "Food Allergies," 1998; 12(5):1-2. J Vet Intern Med, 2001;15(1):7-13. J Am Vet Med Assoc, 1993;203(2):259-62. J Am Vet Med Assoc, 1992;200(5):677-80. J Am Vet Med Assoc, 1991;198(2):245-50.