biostudies-literatureUnknown93(4)von Spreckelsen BThe Danish Environmental Protection Agency under the Ministry of Environment of DenmarkNickel is the most frequent cause of allergic contact dermatitis in Europe and worldwide despite 20 years of regulation. The aim of this study is to systematically assess (i) the risk of nickel allergy associated with piercings and (ii) the proportion of earrings for piercings on the market that release excessive amounts of nickel. The databases PubMed, Embase, and Web of Science were searched. Regarding (i): nickel allergy was significantly associated with piercings in the general population (OR 5.9 [95% CI: 3.6-9.4], n = 5333) and in dermatitis patients (OR: 3.6 [95% CI: 2.3-5.8], n = 20 330). The etiological fraction was 82% (95% CI: 55.2%-92.8%) and 69.7% (95% CI: 62.7%-75.3%), respectively. Regarding (ii): critical nickel release, as determined by dimethylglyoxime (DMG) screening, wasContact dermatitis275-284https://www.ebi.ac.uk/biostudies/studies/S-EPMC12415668biostudies-literatureNickel Allergy and Piercings: A Systematic Review and Meta-Analysis.PMC12415668Johansen JDAhlstrom MGJensen MBvon Spreckelsen BfalseNickel Allergy and Piercings: A Systematic Review and Meta-Analysis.Nickel is the most frequent cause of allergic contact dermatitis in Europe and worldwide despite 20 years of regulation. The aim of this study is to systematically assess (i) the risk of nickel allergy associated with piercings and (ii) the proportion of earrings for piercings on the market that release excessive amounts of nickel. The databases PubMed, Embase, and Web of Science were searched. Regarding (i): nickel allergy was significantly associated with piercings in the general population (OR 5.9 [95% CI: 3.6-9.4], n = 5333) and in dermatitis patients (OR: 3.6 [95% CI: 2.3-5.8], n = 20 330). The etiological fraction was 82% (95% CI: 55.2%-92.8%) and 69.7% (95% CI: 62.7%-75.3%), respectively. Regarding (ii): critical nickel release, as determined by dimethylglyoxime (DMG) screening, was2025-01-01T00:00:00Z2025 Oct2026-06-03T05:58:49.917Z2026-04-25T03:17:00.886ZS-EPMC124156684061158510.1111/cod.14837