Clinical expressions of food allergy

Background: The perception, by both the public and health professionals, of the clinical expressions of food allergy (FA) varies widely, from one extreme of nonexistence to another extreme of causing almost every ailment. Critical investigations in recent years led to a better clarification, as well as a reasonable classification, of FA manifestations. Objective: To provide a differential diagnosis of adverse reactions to foods and a classification of well proven FA manifestations. Data Sources: Reviews and original articles published in peer-reviewed journals, as well as classic textbooks on FA. Results: FA can affect several body systems. The gastro-intestinal tract is probably the most affected organ, but it does not always exhibit overt symptoms. Cutaneous manifestations are next in frequency, and in some studies are the most frequent perhaps because they are visible. Respiratory symptoms as sole manifestations of FA are less common, but have high frequency in children with atopic dermatitis. Systemic anaphylaxis has been responsible for sudden fatalities, although the exposure was often to minute quantities of the offending food. Other rare manifestations have been reported and are probably underdiagnosed. Conclusions: FA is defined as the immunologically mediated adverse reactions to foods. It can be expressed in a wide array of clinical manifestations, ranging from simple gastro-intestinal, cutaneous, or respiratory symptoms to fatal anaphylaxis. Studies are needed to verify some rare or anecdotal manifestations that have been reported but are still considered controversial.