Secular change in the occurrence of atopic dermatitis.

Atopic dermatitis is a common disease, and population-based studies indicate that the frequency of atopic dermatitis has increased substantially during recent decades. It has been generally accepted that disease onset occurs before 7 years of age in 80-90% of the cases, and consequently the epidemiology of atopic dermatitis has been studied mostly in children on admission of first grade school. Before 1960 about 2-3% of children suffered from atopic dermatitis. In the 1960s, some 4-8% was recorded in several studies, and for those born after 1970 most researchers found that 9-12% developed atopic dermatitis during childhood. The diagnostic criteria of Hanifin and Rajka are cumbersome for population studies not designed specifically for children. In order to compare epidemiologic data from varying times and locations, a framework for questionnaire studies in atopic dermatitis is proposed.