Milestones in understanding allergy and its diagnosis

Abstract

SummaryThe prevalence of allergic conditions continues to increase, affecting up to 40% of the population in some countries. Our understanding of the processes of allergy began in 1869, when Blackley first connected hay fever with pollen. In 1911, Dale and Laidlaw discovered that histamine was the principal mediator of anaphylaxis. This led to the development of the first antihistamine, in 1942. In 1968 the WHO International Immunoglobulin Reference Centre officially declared the discovery of IgE based on the work of Bennich, Ishizaka and Johansson. The importance of IgE in allergy is such that the definition of allergic disease is based on the presence of allergen‐specific IgE. Access to IgE allowed experimental, immunochemical studies in vitro. Research activity in the field of immunology increased enormously and generated more important knowledge, including the discovery and characterization of leukotrienes, cytokines and histamine receptors. The involvement of other cells in the allergy process was described. In parallel with the elucidation of the processes involved in allergy came the development of new drug treatments. The first anti‐allergy agents were the antihistamines. Later came sodium cromoglycate and corticosteroids. Immunotherapy was first used in the early 1900s but became less popular with the development of anti‐allergy drugs. Now, however, there is a resurgence of interest in the technique. The discovery that there are two subtypes of T‐helper (Th) cells, which produce different cytokines, and that the Th2 subtype appears to produce cytokines associated with allergy has opened new avenues of research that hold promise for reducing the prevalence of allergy in the population, either by preventing its development or by treatments that can drive the immune system towards a Th1 bias.