Is It a Food Allergy?

 — OR A DIFFERENT PROBLEM?

 An astonishing number of people now have food allergies — not. A number of recent studies have found that most people who believe they have food allergies actually don’t — one small study puts that figure as high as 90%! This state of affairs led the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, to release new guidelines to provide a uniform strategy for diagnosing and managing food allergies. I spoke with Matthew Fenton, PhD, chief of the asthma and allergy branch of NIAID, to find out more…

 WHAT’S YOUR REAL PROBLEM?

 The new guidelines, which you can see on The Journal of Allergy and Clinical Immunology Web site at www.JACIOnline.org/article/S0091-6749(10)01566-6/fulltext, define a food allergy as “an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food.” Or, in easier-to-digest language, most food allergies result from a mistaken response by the immune system, which identifies something you eat as a threat and then creates antibodies to attack it and fight it off. These antibodies usually are what create the allergy symptoms. But, Dr. Fenton told me, what many (if not most) people call food “allergies” are actually more accurately described as “intolerances,” especially in the case of lactose, food dyes and chemicals such as MSG.

What’s the difference? Intolerances are not caused by the immune system, and they tend to be complex reactions (for instance, causing stomach upset and/or headaches) that worsen as you eat more and more of the food. Allergies, on the other hand, cause symptoms such as redness, itching, tightness in the throat, shortness of breath or anaphylactic shock. Both are troublesome, but it’s important to identify whether your reaction is an allergy or intolerance because the two have different consequences — allergies are dangerous while intolerances are merely terribly unpleasant. And they require different treatments.

 WHAT IT ALL MEANS

 If you suspect that you have a food allergy — or if you now suspect that you don’t have a food allergy, but rather an intolerance — discuss your concern with your doctor. A detailed medical history and perhaps a skin prick test and/or blood antibody test will help distinguish between intolerance and allergy.

Important! Tests are done on extracts, which are purified, as opposed to foods, which often contain multiple ingredients. Therefore, a negative result to a test using an extract is not really definitive. It is important to be aware that in the real world, foods may contain other ingredients that you may or may not know they contain. Meanwhile, a positive result does not necessarily confirm an allergy. It means that you have a sensitization to a food that could be either an allergy or an intolerance.

 THE TRUE TEST

 For these reasons, Dr. Fenton suggests that people who believe they have food allergies should get confirmation by having a tightly controlled oral challenge performed by an allergist in a setting where he/she has access to medications and equipment to treat severe reactions. You will be instructed to avoid the suspected food for a certain length of time (usually an hour or two) before your appointment. Then, while you are in the doctor’s office, you will consume gradually increasing amounts of the food. Your doctor will monitor your reaction to determine whether you have an allergy or intolerance and, of course, will be able to provide appropriate treatment if your reaction veers into dangerous territory. Since there are no FDA-approved treatments for food allergy at present, you will then have to avoid the food that you are allergic to.

It’s good news to learn that foods you are intolerant of — but not allergic to — aren’t truly dangerous to your health but, of course, an intolerance produces unpleasant symptoms itself, so it makes sense to follow the very same advice — eat something else.

Source: Matthew J. Fenton, PhD, division of allergy, immunology and transplantation, National Institute of Allergy and Infectious Diseases, National Institutes of Health,Bethesda.

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