Recently I have been asked about “food intolerance” as measured by IgG. This is a blood test, usually mailed to an office suite address somewhere, which returns with “Foods to Avoid” for numerous maladies including arthritis, headache, fatigue, and you name it. I don’t think anyone tests totally “negative”. IgG antibodies (IgE are allergic antibodies) which attach more or less to foods have been studied for perhaps 25 years. Like most of these touted tests and treatments, there is a grain of truth. IgG is involved with gluten protein in celiac disease, a usually severe chronic bowel disorder. It is my opinion that IgG has not been reliably connected to other disorders when studied in a rigorously controlled double blind fashion.
Indeed, we all make a little IgG antibody and it varies week to week. There’s frequently poor agreement of results among various laboratories sent the same sample. The field of allergy seems to draw more than its share of unproven or downright merit less treatments. I would suggest the link below.