TY - CHAP M1 - Book, Section TI - Allergic Disease and Atopy A1 - Davis, Carla M. A1 - Chatila, Talal A. A2 - Kline, Mark W. PY - 2018 T2 - Rudolph's Pediatrics, 23e AB - A precipitous increase in incidence and prevalence of allergic diseases in the last 50 years has led to the current pandemic proportions. In some subpopulations, as many as 1 in 4 children suffers from asthma, and up to 1 in 12 has a food allergy. One explanation for this dramatic increase in allergic diseases is the “hygiene hypothesis,” which posits that a decrease in the exposure to microbes due to improved hygiene, smaller families, less breastfeeding, more immunizations, and lack of serious childhood infections results in altered immunoregulation and deviation toward an allergic disease-promoting T-helper cell 2 (TH2) response. Microbial exposure promotes the production of regulatory T cells involved in maintaining tolerance to allergens. Lack of sufficient microbial exposure may result in weakened tolerance and, in the setting of other factors such as genetic predisposition and environmental exposures, result in the promotion of allergic diseases. The important environmental exposures that can directly decrease microbial diversity, causing increased expression of atopy, include urbanization, industrialization, climate change and rising temperatures with prolonged pollen seasons, increased viability of mold, and increased aeroallergen exposure. The increased prevalence of allergic disease is directly related to these factors. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/11/09 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1182931734 ER -