Hypersensitivity reactions to food proteins are rare, probably because the intestinal immune system has evolved efficient means of preventing such responses. In this article Allan Mowat reviews the mechanisms underlying the induction of immunological tolerance after feeding proteins and suggests how a breakdown in oral tolerance may lead to potentially harmful hypersensitivity in the intestine.

The intestinal immune apparatus has to mount rapid and potent effector response~ to prevent invasion by pathogenic viruses, bacteria and other parasites. Yet despite the numerous potential antigens in a normal diet, hypersensitivity reactions to dietary constituents are uncommon. The intestinal immune system seems, therefore, to have evolved means of preventing hypersensitivity to orally administered antigens. This article will review some of the mechanisms which regulate immune responses to dietary proteins and indicate how a breakdown in this homeostatic system may lead to disease.