The relevance of anti-food antibodies for the diagnosis of food allergy.

All individuals are exposed to large amounts of potentially immunogenic food proteins. Most people respond by producing IgG, IgA, or IgM antibodies. The presence of such antibodies in serum is a normal, but not necessarily physiologic phenomenon. In certain groups of individuals, such as young infants, persons with a selective IgA deficiency and patients with inflammatory gastrointestinal disorders, especially high levels of such antibodies are commonly found despite complete tolerance to intake of the food in question. Obviously the finding of IgG, IgA or IgM antibodies to food proteins in serum is of limited clinical relevance. The presence in serum of IgE antibodies to food antigens is not uncommon in some patients with atopic dermatitis, although the clinical relevance of the antibodies for the dermatitis is not always clear. Young, atopic children have low levels of such antibodies as a normal, transient phenomenon. High concentrations of IgE antibodies not only to classical food antigens such as egg, fish, cow's milk, nuts, shellfish, peanuts and cereals but also to less typical allergens such as celery, some spices and other vegetables often indicate a pronounced food allergy that can give rise to a serious reaction upon contact. In contrast to the case with non-IgE antibodies, the presence of IgE antibodies in serum is a non-physiologic state of clinical relevance.