This article has been reviewed by Andrew Moore, MD, FAAAAI
It is very common for patients to feel as if they have food allergies or food intolerances / sensitivities. These terms or labels are often used interchangeably. It is important to understand though, that allergies are very different than intolerances or sensitivities. There are excellent materials on this website to help you distinguish between the two. With a food allergy, the body is making an immune response to the food, and this can be dangerous. With an intolerance or sensitivity, the body may just not be processing or digesting the food appropriately and this is not actually dangerous (although it can obviously be uncomfortable).
The most classic food intolerances (such as lactose intolerance) cause patients to have bloating, fullness, belly pain, gas and/or diarrhea when they eat too much of the food. This is because the body is not properly digesting the food, which leads to build up of air and gas in the stomach and intestines. Other patients feel like they get headaches, fatigue, “brain fog” or belly pain with various foods or additives / preservatives. Many times, patients feel like multiple foods may be causing these symptoms and are hopeful to find a single test that will tell them exactly which foods to avoid so that they can simply feel better.
Unfortunately, no single test exists that can give you this answer. A test that claims to be able to diagnose food sensitivities and is commonly available is the food IgG test. This test, offered by various companies, reports IgG levels to multiple foods (usually 90 to 100 foods with a single panel test) claiming that removal of foods with high IgG levels can lead to improvement in multiple symptoms. Some websites even report that diets utilizing this test can help with symptoms of irritable bowel syndrome, autism, cystic fibrosis, rheumatoid arthritis and epilepsy.
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 The scientific studies that are provided to support the use of this test are often out of date, in non-reputable journals and many have not even used the IgG test in question.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, the Canadian Society of Allergy and Clinical Immunology and the European Academy of Allergy and Clinical Immunology have recommended against using IgG testing to diagnose food allergies or food intolerances / sensitivities.
It is understandably frustrating while looking for ways (especially natural, non-medicinal ways) to feel better, but patients need to know if the advice they are following is based on tests that have been proven or on tests that are controversial and have not been proven. Before someone severely alters their lifestyle and diet, they should have some comfort in knowing that they are doing so based on proper advice. An allergist / immunologist is able to provide you with this advice and can help you properly diagnose and manage your condition.
AAAAI support of the EAACI Position Paper on IgG4. Adverse Reactions to Foods Committee, May 2010
Lavine, E. Blood testing for sensitivity, allergy or intolerance to food. CMAJ 2012; 184(6): 666–668
Choosing Wisely. Don’t perform unproven diagnostic tests, such as immunoglobulin G(lgG) testing or an indiscriminate battery of immunoglobulin E(lgE) tests, in the evaluation of allergy. April 2012
Press Release, AAAAI. JAMA: Inappropriate Allergy Testing Leads to Inappropriate Management, June 2014