Because you’re reading this, chances are you’ve done some online searching related to food allergies. Maybe you’ve googled for recommendations for an allergist in your area, for an allergy-friendly cookie, or for a cream to help with your eczema.
If you have, you’ve probably noticed tons of ads for companies that provide at-home food intolerance testing. What’s that all about and should you look into it?
Before we talk about these services, it’s important to understand the difference between a food allergy and a food intolerance.
With a food allergy, your body has developed an immune reaction to a food that can be serious, even life-threatening.
How it does this is by creating Immunoglobulin E (IgE) antibodies specific to the foods you are allergic to. When the antibodies bind with proteins from that specific allergen, it sets off a cascade of immune responses that may result in a number of classic symptoms including rash, hives, swelling, breathing difficulties, etc.
Testing for a food allergy is done via skin prick — where a diluted form of the allergen is inserted into the skin — or blood testing where the IgE for various allergens is measured in the lab.
A food intolerance (e.g. lactose intolerance) on the other hand causes an individual to experience bloating, fullness, belly pain, gas, and/or diarrhea when they eat too much of a specific food, usually because their body is not properly digesting the food leading to a build-up of air and gas in the stomach and intestines. Patients with an intolerance to foods often complain of headaches, fatigue, and brain fog as well, symptoms that may overlap with those of an allergic reaction.
But what food could be triggering the symptoms of intolerance? That’s generally determined by omitting foods one by one to see if the symptoms don’t reappear, a time-consuming, often frustrating prospect.
So many people are enticed by the plethora of home food intolerance/sensitivity tests that have flooded the market. These often advertise testing for 100 or more foods with a single kit that can be administered from the comfort of your home.
These work similarly to IgE blood tests except they look for another type of antibody: Immunoglobulin G (IgG).
IgG is a “memory” antibody that indicates that you have been exposed to a foreign protein in the past. These intolerance tests look for elevated levels of IgG to specific foods and report these as possible triggers of symptoms.
The problem is that the presence of IgG has never been shown to be a reliable predictor of intolerances/sensitivities to foods.
The American Academy of Allergy, Asthma, and Immunology (AAAAI) sums it up this way:
It is important to understand that this test has never been scientifically proven to be able to accomplish what it reports to do. The scientific studies that are provided to support the use of this test are often out of date, in non-reputable journals and many have not even used the IgG test in question. The presence of IgG is likely a normal response of the immune system to exposure to food. In fact, higher levels of IgG4 to foods may simply be associated with tolerance to those foods.
Due to the lack of evidence to support its use, many organizations, including the American Academy of Allergy, Asthma & Immunology and the Canadian Society of Allergy and Clinical Immunology have recommended against using IgG testing to diagnose food allergies or food intolerances/sensitivities.
To put it another way, Don’t Buy Into the Hype. It makes no sense to shell out several hundred dollars for a test that is not backed by reliable, independent, peer-reviewed research, and may actually lead you to avoid foods that do not cause symptoms.