When it comes to differentiating between an allergy and a senstivity or intolerance, not all tests are created equal.
Traditional allergy tests register positive only when a food or other toxicant triggers an antibody called immunoglobulin E, or IgE. The presence of IgE in the body tells cells to produce histamines “with explosive force,” says Leo Galland, MD, a New York City–based functional-medicine practitioner. It is that instant flood of histamines that is responsible for the acute symptoms of an allergy, from sneezing and eye-watering to full-blown anaphylaxis. (Anyone who has been relieved of an acute allergic reaction by antihistamine drugs understands the IgE reaction intimately.)
But some irritants don’t trigger the IgE antibody pathway — and, hence, don’t show up on conventional allergy tests. Instead, they trigger the immunoglobulin G, or IgG, pathway, which leads to inflammatory symptoms like migraines, joint pain and arthritis, and abdominal pain. The most likely triggers for this pathway are particular foods. These reactions are often called sensitivities or intolerances rather than allergies, as they involve a subtler, nonhistamine reaction.
IgG reactions are difficult to detect because symptoms can set in up to 24 hours after exposure — and sometimes longer. When there’s a gap that long between a trigger and a stomachache or migraine, it can take some sleuthing to work out the cause. If you suspect a hidden intolerance or sensitivity, find a practitioner who tests for and treats IgG-type sensitivities. Those tests may include fecal and breath tests.
You can also try an elimination diet to see if it offers relief from digestive and other symptoms. (Download the elimination diet guide from the Institute for Functional Medicine at ELmag.com/ifmdetox.)
This originally appeared in “Taking on the Allergy Epidemic” in the April 2017 issue of Experience Life.