Q: How do allergists determine if a child has outgrown a food allergen? Is testing safe and effective?
Todd A. Mahr, MD: Assuming the child has a confirmed food allergy diagnosis, what allergists are going to do is follow an allergen-specific immunoglobulin E (igE) blood test. This test will identify a food allergy by measuring levels of different IgE antibodies in the blood that protect the body from allergens.
And then ideally allergists are going to do an oral food challenge in the office. An oral food challenge involves having a patient eat a tiny amount of the suspected food allergen, and if there’s no reaction, the amount of food is gradually increased to determine if it triggers an allergic reaction.
Oral food challenges should only be done under medical supervision. The tests are safe and effective, but because they involve exposing a patient to a food allergen, there is a risk of life-threatening anaphylaxis.
What about skin prick testing? It won’t help – skin test results for food allergies have been shown to be positive even after someone has outgrown a food allergy.
A lot of parents want to know at what age their child might start to outgrow a food allergy. We can’t give them a time – or a time range. It will depend on the child and the individual food allergen. It’s more common to outgrow allergies to cow’s milk, egg, soy and wheat. It’s less likely to outgrow allergies to peanuts, tree nuts, fish and shellfish.
Parents often come to believe their child has outgrown a food allergy after an accidental exposure at home. Hopefully they had epinephrine auto-injectors and an Allergy and Anaphylaxis Emergency Plan on hand, and they were able to avert a life-threatening reaction. This exposure can alert parents and doctors that maybe the child is outgrowing the food allergy, or the process is occurring.
What we don’t want is parents conducting an oral food challenge on their child at home, without medical supervision.
An oral food challenge should be conducted in a medical facility by an allergist who is well trained and experienced in food allergies and anaphylaxis. It should be done with supplies of epinephrine, oxygen, IV fluids and other emergency treatments for anaphylaxis readily available.
Speak with an allergist if you have specific questions about your child’s food allergy or undergoing an oral food challenge.
Todd A. Mahr, MD, FACAAI, is an allergist and immunologist in La Crosse, Wisconsin. He is President-Elect of the American College of Allergy, Asthma & Immunology (ACAAI) and Immediate Past Chairperson for the American Academy of Pediatrics Section on Allergy and Immunology.
Have a medical question? Email editor@allergyasthmanetwork.org or write to Ask the Allergist, Allergy & Asthma Network, 8229 Boone Blvd., Suite 260, Vienna, VA 22182.
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