Nickel allergy is associated with wheezing and asthma in a cohort of young German adults: results from the SOLAR study

Nickel allergy is the most prevalent contact allergy. It belongs to a different hypersensitivity type to asthma and rhinoconjunctivitis. The aim of this analysis was to assess whether self-reported nickel allergy is associated with incident wheezing, asthma and rhinoconjunctivitis in young German adults, taking into account potential effect modification by sex. In total, 2051 (70.6%) participants aged 19-24 years took part in the second phase of SOLAR (Study on Occupational Allergy Risks), a follow-up study of ISAAC II (the second phase of the International Study of Asthma and Allergies in Childhood) in Germany. Self-reported nickel allergy, as well as having pierced ears, and the three outcomes incident wheezing, asthma and rhinoconjunctivitis, were analysed stratified for sex. Logistic regression adjusted for potential confounders was performed. An association between self-reported nickel allergy and incident wheezing was observed for men and women, while only in males did pierced ears show a significant association with the outcome (adjusted OR 2.26, 95% CI 1.10-4.62). Also only in males, self-reported nickel allergy was associated with elevated odds for incident asthma (adjusted OR 4.34, 95% CI 1.22-15.41). Neither in men nor in women was a significant association observed for incident rhinoconjunctivitis. Our results suggest that self-reported nickel allergy is associated with incident wheezing. Whether this association is due to environmental or genetic predisposition, or due to an overlap of the mechanisms of type I and type IV hypersensitivity, needs to be elucidated.