Changes in the seasonal dependence of atopic dermatitis in Japan.

Although it has been generally accepted that seasonal aggravation of skin symptoms is a basic feature of atopic dermatitis, recent studies have suggested a decrease in the seasonal dependence of the dermatosis in European countries over the past several decades. We examined incidence of seasonal deterioration of atopic dermatitis in Japanese subjects. The study population consisted of 682 patients aged 3 to 30 years with atopic dermatitis, who visited our outpatient clinic from August 1998 through July 2000. Of these, 452 (66%) showed a seasonal aggravation of skin symptoms, and 230 (34%) had perennial deterioration. The overall incidences of exacerbation in spring, summer, autumn and winter were 25%, 19%, 11% and 36%, respectively. Further, 358 (52%) showed unpredictable and irregular exacerbations of skin symptoms every few days or weeks. These irregular worsenings were more frequent in patients who showed perennial deterioration than in those with seasonal aggravation. From a comparison of the present results with those reported in the 1960s, it became evident that a real decrease in the incidence of seasonal aggravation of atopic dermatitis has occurred over the past three decades in Japan and that the incidence of summer deterioration has greatly decreased during the same period of time.