Immune responses to environmental antigens absorbed through the gastrointestinal tract

Foods, food additives, beverages, drugs, and intestinal microorganisms are potentially important sources of environmental antigens. While proteins taken orally ordinarily are absorbed to only a limited extent, under appropriate circumstances enough absorption occurs to produce an immune response. Acute allergic reactions to foods are not uncommon and as a rule are mediated by IgE antibodies. The possibility that small quantities of food antigens absorbed over a period of years without acute symptoms of allergy might produce a cumulative systemic or local immunological toxicity remains to be convincingly demonstrated.