Where to Turn After Diagnosis of Multiple Food Allergies

June 1, 2008

A patient of mine recently had an extensive allergy workup after a rash developed, apparently following exposure to wheat products.

A patient of mine recently had an extensive allergy workup after a rash developed, apparently following exposure to wheat products. The workup indicated multiple allergies to practically all grains as well as to a multitude of vegetables and fruits. The list of allergic reactions that seem to have been elicited by skin testing is so extensive that the patient's food consumption is threatened. Is there a centralized agency where suitable specialized diets can be obtained, or is some form of therapy available?

----- MD




There are really 2 issues here. First, assuming that your patient is truly allergic to all these foods, there is no centralized agency that provides appropriate diets. Thankfully, food allergy is now a large enough business that many Web-based companies and specialty food stores provide specialized products-a great improvement over the situation just 10 years ago. However, these products, such as nut- or gluten-free items, are principally for persons who are allergic to a specific food, rather than for persons who are following comprehensive avoidance diets.

Second, and even more important, is that the entire diagnostic evaluation ought to be reconsidered. Although testing for food allergy can be quite helpful, it is a very inaccurate science. Negative test results are likely to be accurate, but positive results are often false-positive. In fact, the positive predictive value of food allergy skin testing in most studies is less than 50% (ie, more than 50% of positive test results will ultimately prove to be incorrect).

The only true test for a food allergy is what happens when the patient eats the food. Some food allergies can be low-grade and chronic, such that a clear cause-and-effect relationship between the consumption of the food and the development of symptoms may not be evident. However, if no symptoms occur-as might be the case for your patient with some of the grains or fruits or vegetables on his or her list of foods to avoid-then some of the test results were likely wrong. In any event, I would recommend a second opinion, ideally from an allergist with special expertise in food allergy who can conduct oral food challenges. Food challenges remain the gold standard for the diagnosis of food allergy.

----- Robert A. Wood, MD
Professor of Pediatrics and International Health
Director, Pediatric Allergy and Immunology
Johns Hopkins University School of Medicine
Baltimore