This test detects the presence and level of IgG against food digested proteins in serum. Some of these not fully hydrolysed high molecular weight molecules can cross the enteric epithelial barrier and, entered the bloodstream, are recognized by the immune system both as allergens as common antigens.
Sometimes they cause an anaphylactic IgE-mediated reaction (food allergy), but more commonly they result in a slow chronic IgG-mediated immunization, often not decreased but even increased by food cooking. With growing evidence, a high levels occurrence of these antibodies is sometimes associated with alimentary disorders (such as abdominal pain, diarrhea, and nausea) and syndromes (such as headache) requiring a temporary or permanent suspension of certain foods consumption.
The test can identify specific foods that cause the so-called "non-IgE allergies", a condition distinct from food (IgE) allergies and food (metabolic) intolerances.
Food antigens, separately adsorbed on well surface, react with serum IgGs, if present in the sample. After washing to remove unbound molecules, the captured IgGs are recognized by an enzyme-labeled secondary antibody, that thencatalyzes its chromogenic substrate. The colorimetric reaction is compared against a human IgG standard curve.