Evaluating Allergies and Food Reactions
March 2, 2016
David Berger, MD, FAAP
Question: What is your approach to evaluating allergies and food reactions?
Answer: We frequently get asked about allergy testing. Unfortunately there is not a simple answer because there are many types of sensitivities, each requiring its own lab test. Furthermore, these tests are not 100% reliable.
Let me start by explaining that the term “allergy” only represents one type of negative reaction, called “IgE”, which causes the release of histamine.
The standard blood test done at labs screens for the individual IgE to the potential allergen. Skin tests look for a small hive that is formed as a response to the IgE/histamine reaction. If either of these tests are positive, there is a good possibility that their is an allergy to that food or environmental exposure.
There are other types of negative reactions that a person can have. IgG reactions are also referred to as “delayed hypersensitivity” and take up to 3 days to produce a reaction. Usually this does not bring a histamine/allergy reaction, but can affect behavior, mood, or GI symptoms.
White blood cell reactions can also be checked. If the white blood cells swell in the presence of a food antigen, there could be a negative reaction in the body.
Celiac disease, which is a form of gluten sensitivity, is usually an IgA reaction
Not all negative reactions are immune-based. With a lactose intolerance, or sometimes with casein or gluten issues, a person has a faulty digestive enzyme, and the lack of digestion of a protein or sugar can cause some people symptoms.
Due to all of this, we feel the pan-ultimate way of checking for a food reaction is through an elimination-reintroduction diet, where a person avoids a list of foods for a few weeks then brings them back one at a time to look for a reaction.
We provide details of how to do this method in our article, Elimination Diet for Food Allergies and Sensitivities, which you can find in the medical topics section in our website resources. When this test is done properly, a negative reaction to a food can be identified, regardless of which of the above types of reactions is occurring.
Note: This information is not intended to replace consultation between a patient and medical provider. It is for general purposes only.