The original hygiene hypothesis proposed that reductions in family size and exposure to childhood infections were responsible for the rise in atopic diseases. Numerous epidemiologic and longitudinal studies have been performed to test this hypothesis, which has evolved in response to these findings and emerging concepts related to the innate immune response and immunoregulatory mechanisms. Collectively, these advances raise hope that the concepts espoused in original hygiene hypothesis may soon lead to new preventive approaches to atopic diseases.
Department of Pediatrics, University of Wisconsin-Madison, K4/910 CSC, 600 Highland Avenue, Madison, WI 53792–9988, USA
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Supported by NIH grants R01HL61879-01, P01HL70831-01, and 5M01 RR03186-18.