Many people managing food allergies understand that allergy is an immune system response to a specific food.
What people may not realize is that allergic reactions fall into one of two categories, each mediated by a different aspect of the immune system:
- One type of allergy involves immunoglobulin E (IgE) and is called an IgE mediated reaction.
- The second allergy type does not involve IgE, and is aptly called a non-IgE mediated reaction.
The difference between IgE and non-IgE responses is important to know when discussing allergy testing with your doctor.
The Two Responses
A non-IgE mediated reaction involves the immune system’s T-cells, not IgE antibodies. This type of reaction usually causes a delayed onset of symptoms after ingesting a particular food. The delay can be hours or days.
Non-IgE reactions typically disturb the gastrointestinal tract with symptoms that include upset stomach, vomiting, diarrhea, and bloody stools. Anaphylaxis does not occur in non-IgE allergy.
An IgE mediated reaction is what doctors and researchers typically refer to as “food allergy.” When food-specific IgE antibodies form and latch onto the body’s allergy cells, eating the specific food triggers an onset of allergic symptoms. The onset is usually immediate but may be delayed up to three hours.
The symptoms of IgE reactions include swelling, hives, watery/itchy nose or eyes, breathing difficulty, trouble swallowing, and vomiting. Anaphylaxis may occur.
Types and Tests
The difference between the IgE and non-IgE reactions explains why determining whether a child has an allergy starts with a thorough medical assessment, and not allergy testing.
A detailed history of suspected foods, the timing of symptoms, which symptoms occur, and the effects of any attempted treatments will determine whether an IgE mediated allergy is likely. If the history suggests a non-IgE allergy, running tests for the IgE antibody (e.g., skin-prick, IgE blood tests) will not be useful.