Internal and external environmental influences in allergic diseases.

Allergy defines the hypersensitivity reactions caused by allergen-specific immunoglobulin E binding to mast cells, being cross-linked by subsequent allergen exposure, and releasing mediators of immediate hypersensitivity that initiate inflammatory cascades. Allergic diseases have both genetic and environmental components. Growing concern about allergic disease comes from the observed increase in incidence and prevalence and association with the development of asthma. This risk appears to be compounded by Western lifestyle, including indoor environment, diet, air pollution, and psychological stress. With increasing understanding of these mechanisms, new and improved modes of therapy are being developed to manage and possibly prevent allergic sensitization.