Decrease in nickel sensitization in a Danish schoolgirl population with ears pierced after implementation of a nickel-exposure regulation.

BACKGROUND: To reduce the skin nickel exposure of the population, the Danish Ministry of Environment issued a regulation that was implemented in 1992, and the European Union countries have recently adopted an expanded regulation.
OBJECTIVES: The aim of our combined patch testing and questionnaire investigation of girls in public schools and high schools/production schools was to evaluate whether the regulation has had an impact on the prevalence of nickel sensitization.
METHODS: To find a group of girls with ears pierced mainly after implementation of the nickel-exposure regulation in Denmark, girls were recruited from the fifth and sixth grade in 12 public schools (the public school group). After the public school level almost all girls from a public school population continue their education in high schools or other schools such as production schools or technical schools. Therefore, to find girls demographically similar to the public school girls but older, and with ears pierced before implementation of the regulation, girls from seven high schools and two production schools were recruited (the high school group). Four hundred and twenty-seven girls in the public school group (mean age 12.4 years, range 10-14) and 534 in the high school group (mean age 18.8 years, range 17-22) participated. All participants filled out a questionnaire concerning ear piercing, use of oral braces and former patch testing for nickel sensitivity. Three hundred and five girls (71.4%) in the public school group and 275 (51.5%) in the high school group were patch tested or had been tested previously and the results of these tests were included in the study. The relation between the frequency of nickel sensitization and the various factors that might influence the prevalence of nickel sensitization was evaluated by multivariate logistic regression analysis. The investigation was conducted from March 1999 to March 2000.
RESULTS: The study showed that both increasing age and having ears pierced before 1992 enhanced the prevalence of nickel sensitization. We found that 17.1% of the girls in the high school group demonstrated a positive patch test reaction to nickel. In contrast, the prevalence of nickel sensitization in the public school group was only 3.9%. Comparing girls with and without pierced ears, the prevalence of nickel sensitization was significantly higher in girls with ears pierced before, but not after, 1992 (odds ratio 3.34 and 1.20, respectively). Only in the high school group was there a tendency that wearing oral braces before ear piercing had a protective effect on nickel sensitization, but this did not reach statistical significance.
CONCLUSIONS: As we found an effect of ear piercing before but not after 1992, this study strongly suggests that implementation of the nickel-exposure regulation in 1992 in Denmark has had the intended effect of protecting the female population from becoming allergic to nickel.