Atopic dermatitis: the “Hygiene hypothesis” today
Corazza M; 101-103

The past 20 years have shown a significant rise in the prevalence of allergic diseases in industrialized countries. Atopic dermatitis, in particular, has increased 2 to 3-fold in the last 3-4 decades. It has been supposed that environmental modifications have played a relevant role in increasing allergic pathologies. In 1989 the “hygiene hypothesis” was formulated; it suggested that fewer infections in childhood and a lower microbial burden could promote atopic responses and increase prevalence. Numerous epidemiological studies have provided evidence supporting the hypothesis that a poor standard of living, large household size, farm residence and a lower use of antibiotics may have been protective against atopic diseases and atopic dermatitis. Furthermore, immunologic studies have provided an immunological basis to the hygiene hypothesis. We present a revision of the literature and discuss recent findings regarding the hygiene hypothesis.