Historical background, definitions and differential diagnosis.

Although awareness that food can cause adverse symptoms and even death in some individuals has been present since the times of Hippocrates, it was not until the seminal experiment of Prausnitz that the investigation of food allergy had a more scientific basis. In the first half of the 20th century, there were periodic reports in the medical literature describing various food allergic reactions. Until the studies of Charles May and colleagues in the mid- to late '70s, there was a great deal of skepticism in the medical world about the relevance of food allergy and how to diagnose it, since standard skin testing was known to correlate poorly with clinical symptoms. With the introduction of the double-blind, placebo-controlled oral food challenge by May, the study of food allergy has become evidence based, and tremendous strides have been made in the study of basic immunopathogenic mechanisms and natural history as well as in the diagnosis and management of food allergies. Today, various IgE- and non-IgE-mediated food allergic disorders have been well characterized, and efforts to reverse these allergies using various immunotherapeutic strategies are well under way.