Prevalence, incidence rates and persistence of contact allergy and allergic contact dermatitis in the Odense Adolescence Cohort Study: A 15-year follow-up

Background A cohort of 1501 unselected 8th grade schoolchildren was established 15 years ago with the aim to follow the course of contact allergy and allergic contact dermatitis (ACD) from school age into adult life. To date no studies have evaluated incidence rates and persistence of contact allergy and ACD in an unselected population from adolescence to adulthood. Objectives To estimate the incidence rates and persistence of contact allergy and ACD from adolescence to adulthood, and the point prevalence in adulthood. Methods In total, 1206 young adults from the cohort were contacted and asked to complete a questionnaire and participate in a clinical examination including patch testing with TRUE Test®. The questionnaire was answered by 899 (74.6%), however, only 442 (36·7%) of those invited participated in patch testing. Results Over the 15-year period the incidence rates of contact allergy and ACD were 13·4% and 7·8%, respectively. The point prevalence of contact allergy was 20·1%, and present or past ACD was found in 12·9% of those followed. Nickel was the most common contact allergen (11·8%), followed by cobalt (2·3%), colophony (2·0%), thiomersal (1·4%) and p-phenylenediamine (1·1%). Most nickel reactions were persistent, and a significant number of new nickel sensitizations were found. Fragrance mix I reactions from adolescence could not be reproduced. Conclusions From adolescence to adulthood the incidence rates of contact allergy and ACD were high. Nickel was still the most common contact allergen, and new sensitizations occurred despite the European Union nickel regulation. Fragrance mix I was a poor marker for history of eczematous skin reaction to perfumed products.