Hand eczema is a recurrent chronic skin disease related to contact allergy and atopic dermatitis. When possible, efforts should be redoubled to eliminate provoking factors. Our objective was to assess changes in the prevalence of self-reported hand eczema and to evaluate the association between contact allergy and hand eczema among adult Danes before and after nickel exposure regulation in Denmark. In 1990 and 1998, random samples of 15-41-year-old persons were examined in 2 cross-sectional studies of the general population in Copenhagen, Denmark. The studies included questionnaires, patch and prick testing. From 1990 to 1998 the prevalence of a history of hand eczema increased significantly. This increase did not appear to be fully explained by changes in the prevalence of flexural eczema, prick test reactivity, patch test reactivity, and nickel allergy. In 1990, nickel allergy and allergic nickel contact dermatitis were significantly associated with a history of hand eczema among women. In 1998, these associations were not found. It can be concluded that, from 1990 to 1998, the prevalence of a history of hand eczema rose significantly. It was indicated that it might be possible to prevent the hand eczema related to nickel allergy by exposure regulation, public education or both.