Q: I want to get my daughter tested for food allergies. Is there a test that is more reliable? Which do you recommend?
Martha White, MD: First, schedule an appointment with an allergist who can determine whether your child’s medical history is consistent with a possible food allergy. The allergist can then determine the specific allergens to test.
Allergy testing for foods can be done either by skin prick testing, or by testing the blood for specific IgE directed against the potential food allergen. Both tests provide reliable results, although there’s not always complete agreement in the results between the two tests. I use both tests in my practice.
The skin test provides almost immediate results with a small, localized reaction that you can actually see. I follow up with a blood test that gives an actual IgE level for the food (or other allergen). The blood test can then be tracked every 6-12 months to determine whether or not the child is outgrowing the allergy.
Interpretation of blood test results for food allergy can be tricky. A very low positive result is not always clinically relevant, and an allergist’s input can be helpful in determining which foods should be eliminated from the diet.
If the reactions are restricted to eczema – 40 percent of eczema patients have food allergies – then elimination of those foods that tested positive can be helpful. If the clinical relevance of the positive test is unclear, gradual reintroduction (per your doctor’s instructions) of one food at a time can help determine which foods are contributing to eczema.
However, if the child has experienced an allergic reaction not related to an eczema flare, then reintroduction of a food allergen at home without medical supervision could be dangerous.
In my practice, children with food allergies are prescribed two epinephrine auto-injectors and urged to avoid the food allergen in their diet. We follow the blood test results to determine whether the child is outgrowing the food allergies, and if we think that it may be safe to reintroduce a food, we usually do an in-office food challenge under medical supervision before clearing the child to eat the food at home.
Martha White, MD, FACAAI, is a board-certified allergist at the Institute of Asthma and Allergy in Wheaton, Maryland, a member of Allergy & Asthma Network’s Board of Directors, and a fellow of the American College of Allergy, Asthma & Immunology.
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