IgG Food Testing is an assay that measures IgG antibodies or IgG4 antibodies to foods. This is different from allergy testing which uses IgE antibodies to measure food allergies. Many labs perform IgG food testing and they can accurately measure IgG to food proteins. However the measurement of IgG to foods is promoted to diagnose “food sensitivities” that might manifest as acne, eczema, dry and itchy skin, food intolerance, bloating, fatigue, IBS, joint pain, migraines, respiratory issues, weight gain and/or difficulty losing weight, ear infections, sinusitis or hives. These reactions are labeled as delayed or chronic. The theory promoted by the websites advertising IgG food testing is that the IgG antibodies could lead to these conditions through chronic inflammation perhaps through immune complexes.
But the production of IgG antibodies to foods is a normal immunologic phenomenon. IgG antibodies to foods are found in virtually all healthy individuals. Contrary to the notion that IgG or IgG4 antibodies could lead to food intolerance, the development of these antibodies has been linked to the development of food desensitization or tolerance.
Studies which have shown the utility of IgG food testing have had flawed research protocols. They have not included control groups, they have been retrospective, not randomized or double blinded and they have used ill-defined and subjective measurements of improvement.
A paper by the European Academy of Allergy and Clinical Immunology endorsed by the American Academy of Allergy, Asthma and Immunology states “food-specific IgG4 does not indicate (imminent) food allergy or intolerance, but rather a physiological response of the immune system after exposition to food components. Therefore, testing of IgG4 to foods is considered irrelevant for the laboratory work-up of food allergy or intolerance and should not be performed in case of food related complaints.” The went on to say that positive test results for food specific IgG are to be expected in normal, healthy adults and children. The inappropriate use of this test increases the likelihood of false diagnosis being made and resulting in unnecessary dietary restrictions and decreased quality of life.
Other tests that that have not stood up to scientific rigor for food sensitivities are the ALCAT test, Provocation-Neutralization Testing, Hair Analysis, Electrodermal Testing (EG, VEGA Test) and Applied Kinesiology.
Alternative allergy testing is often expensive and not covered by health insurance and in many cases are unproven or even disproven and none have been demonstrated in appropriate studies to correlate with disease.