Contact allergy in Swedish adolescents : results from the BAMSE cohort study

Sammanfattning: Background: Contact allergy affects about 20-25% of adults in the general population, but it is not completely clear how common it is among children and adolescents. Contact allergy is caused by skin contact to sensitizing substances. Knowledge about the relation between skin exposures, related skin symptoms and contact allergy among children and adolescents is limited. Atopic dermatitis (AD) and filaggrin gene (FLG) mutations have been suggested as risk factors for contact allergy, though this needs to be further explored. Aims: To determine the prevalence of contact allergy at age 16 in a population-based cohort. To determine the prevalence of self-reported skin exposures and skin symptoms at age 16, and assess their association with contact allergy. To assess the association between AD at preschool age and contact allergy at age 16, and the association between FLG mutations and contact allergy, self-reported hand eczema and dry skin at 16 years. Methods: We used data from a Swedish population-based birth cohort (BAMSE), followed from birth to age 16. Adolescents answered questions about skin exposures and skin symptoms at age 16 years. Their parents completed questionnaires at baseline, when the child was 2 months old and then regarding AD at 1, 2, 4, 8, 12 and 16 years. Information about contact allergy was collected by patch test (n=2,285), and FLG mutation status was determined from blood samples at age 16. Results: Contact allergy prevalence was 15.3% among adolescents and higher among girls than boys (17.0% versus 13.4%, p=0.018). Nickel was the most frequent cause of contact allergy (7.5%), followed by fragrance mix I (FM I) (2.1%). Nickel allergy was more common among girls (9.8% versus 4.9%, p<0.001). Many adolescents reported piercing (55.4%) and hair dyeing (50.1%), and girls frequently reported related skin symptoms. Reports of piercing and itchy rash from metal items were associated with increased OR for nickel allergy (adjusted OR 1.77, 95% CI 1.04-3.03 and adjusted OR 2.25, 95% CI 1.57-3.23, respectively). Reported itchy rash from use of makeup or personal hygiene products was associated with increased OR for fragrance allergy (adjusted OR 2.11, 95% CI 1.02-4.35). AD at preschool age was associated with fragrance allergy (adjusted OR 3.10, 95%CI 1.66-5.80), but not with nickel allergy. This association was present among individuals with AD at preschool age with IgE sensitization, but not among individuals with AD at preschool age without. FLG mutations appeared unassociated with contact allergy and hand eczema, but were associated with dry skin at age 16 (adjusted OR 1.50, 95% CI 1.02-2.15). Conclusions: Contact allergy prevalence is high among adolescents in Sweden. Nickel allergy is the most common contact allergy, affecting more girls than boys. Piercing and hair dyeing were reported by the majority at 16 years. More girls than boys reported skin symptoms related to skin exposures. AD at preschool age may be associated with contact allergy to fragrance at 16 years. No association was observed between AD at preschool age and nickel allergy. FLG mutations were associated with dry skin, but not with contact allergy or hand eczema at age 16 years.