Dr. Amy Nett: Great question. I’m glad you asked. I think this is an important point because I do try to be precise when I’m using the words “food allergy” and “food intolerance.” When I think about an allergy, I am thinking about an IgE-mediated process. When you think about an IgE-mediated process, think about the reaction that you get when someone has seasonal allergies. You more often see histamine-mediated symptoms, and IgE-mediated responses may even be hypersensitivity reactions. There’s a huge spectrum because IgE-mediated responses also go to the extreme of anaphylaxis, which, thank heavens, anaphylaxis is incredibly rare, but nonetheless, that’s what I think of when I’m thinking of IgE and/or food allergies. IgE mediated does equal food allergy.
IgG and IgA, which is what we’re testing for with the Cyrex panels, those are food intolerances. I don’t think that we can necessarily say that IgE necessarily equals more severe response than an IgG or IgA response. As you’ve probably seen with some of your patients, IgG and IgA responses can be pretty intolerable for a lot of people, so I would probably get rid of the word “mild” there, and I would say that an IgG and IgA response is a food intolerance. What that manifestation will look like in a patient varies completely, so I would say that an IgG and IgA food intolerance, probably the manifestations or the symptoms are going to be more varied when compared with a true food allergy.
I am very careful with patients when I’m saying we’re going to do food sensitivity testing or food intolerance testing. I try to be clear with them that this is a food intolerance, not a true allergy. Again, there are slight differences in which branch of the immune system you’re triggering and which of those cascades you’re triggering, whether it’s IgE or IgG/IgA. It doesn’t necessarily affect severity. It just affects what the symptoms might look like. And of course, IgE allergies we’re not going to be able to pick up on the Cyrex panels, which test for the IgG and the IgA.