Question: How do we find out if food allergies are causing my child's atopic dermatitis?
Answer: Food allergies can be an important trigger for atopic dermatitis in a subgroup of patients with atopic dermatitis.
These are going to be primarily young children, and several studies now have shown that in children or patients with atopic dermatitis who have persistent, moderate or severe disease, about a third of them will have foods as a triggers for their illness.
To figure this out, we typically go about this by getting allergy prick skin tests to the specific food allergen, or obtain blood to measure specific allergic antibodies to the foods that we want to evaluate.
It's important to remember that a positive test does not prove that a person is clinically allergic.
It just shows that you have these antibodies present. We have found by doing food challenges that positive food skin tests, for example, are only a little bit better than 50-50 in being able to -- in predicting that a food is clinically relevant to that person's illness.
So it's very important to not just obtain allergy tests, but then you need to evaluate them critically and decide what is clinically relevant. In this situation, negative tests done properly usually are able to rule out a food allergy as a trigger.
Positive tests need to be subjected to further evaluation, either through formal food challenges, or possibly through elimination diets. But this should really be done under the supervision of a specialist.