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Thursday, July 2, 2015

The allergy epidemics: 1870-2010

Allergic reactions were virtually unknown prior to 1870, and this is still the case in pre-hygiene villages in parts of the world today. While it has been previously implied that the increase in allergic disease was unimodal, Platts-Mills traces how history indicates this is not the case. Hay fever was first reported in the UK and the United States in 1870, the first clear reports of an increase in pediatric asthma appeared in the 1970s, and the current epidemic of food allergy became apparent in the 1990s. In a fascinating review, Platts-Mills traces the emergence and development of respiratory and food allergies and asthma (J Allergy Clin Immunol 2015; 136(1): 3-13).

Sequential changes in agriculture and trade, hygiene, diet, lifestyle, and environment in the past 150 years have likely contributed to an increase in allergic disease. In England and the US in the latter half of the nineteen century and start of the twentieth century, cultivation of land and the introduction of non-native plant species occurred at the same time that urban centers established clean public water systems. Thyphoid and cholera became rare, and hay fever rose. By the mid-1950s to mid-1960s, the first reports of increasing incidences of asthma appeared, with house dust mites cited as the dominant allergen. Homes during this time were increasingly airtight and carpeted, and with the advent of television children were spending more time inside them. By the 1990s in the US, parents were strongly advised both to avoid giving peanuts to small children and to frequently wash and sanitize children’s hands. Early exposure to peanuts can be protective against the allergy, and it is conceivable that skin permeability to foreign proteins has changed.

Finally, with the influx of technology, we as a culture from childhood forward are increasingly indoors. This has shown consequences including the rise in obesity and decline in physical fitness. The consequences most relevant to the topic at hand are the steady increase in exposure to indoor allergens, the decline in outdoor exposure, and exercise. Changes in environment and lifestyle will likely continue to result in unforeseen allergic developments.

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