Nickel sensitization and ear piercing in an unselected Danish population. Glostrup Allergy Study

The study aimed at evaluating nickel sensitization and ear piercing in an unselected population. A questionnaire and ready-to-apply patch tests (TRUE-Test) were mailed to 793 subjects, aged 15 to 69 years. A total of 567 (71.5% out of the 793) were patch tested. The tests were read 2 days after application. Nickel sensitization was diagnosed in 11.1% of the females and in 2.2% of the males. Independent of sex, old age was associated with a lower risk of nickel sensitization (p < 0.01). The risk of nickel sensitization was independent of a history of flexural eczema (p > 0.5). Ear piercing was more common in the young than in the older age groups, ranging from 30.5% to 0.0% in men, and from 91.5% to 42.9% in women. Sensitization to nickel was found in 14.8% of those with pierced ears as compared to 1.8% among those without pierced ears. When adjusted for the effects of sex and age, the risk of nickel sensitization among those with pierced ears remained significantly increased and the odds ratio value was 4.5; the 95% confidence interval of the odds ratio value was 1.5 to 13.0. The study confirmed that nickel sensitization in the general population is common, particularly among women. Ear piercing is probably an important risk factor for nickel sensitization.