title: Fluctuations in the prevalence of nickel and cobalt allergy in eczema patients patch tested after implementation of the nickel regulation in Denmark.
abstract: BACKGROUND
  A recent Danish study showed that the prevalence of nickel allergy decreased among young female patients and increased among older female patients with dermatitis patch tested between 1985 and 2007 at Gentofte Hospital, Denmark. The prevalence of cobalt allergy remained unchanged.
  
  
  OBJECTIVE
  To examine fluctuations in the prevalence of nickel and cobalt allergy after implementation of the nickel regulation, by analysing patch test results from male and female patients with dermatitis tested between 1992 and 2009 at Odense University Hospital, Denmark.
  
  
  METHODS
  A retrospective analysis of patch test data was performed (female, n = 5821; male, n = 3317). Comparisons were made using the chi-square test for trend. Logistic regression analyses were used to test for associations.
  
  
  RESULTS
  The prevalence of nickel allergy decreased significantly among the 2-30-year-old female patients, from 29.8% in 1992-1997 to 19.6% in 2004-2009 (p < 0.001), whereas it increased significantly, from 6.9% in 1992-1997 to 11.1% in 2004-2009 (p = 0.04), among the >60-year-old female patients. The overall prevalence of cobalt allergy increased significantly, from 3.7% in 1992-1997 to 5.1% in 2004-2009 (p = 0.03). The overall prevalence of nickel and cobalt allergy among male patients during the test period was 5.2% and 2.2%, respectively, and no significant change across the test years was detected.
  
  
  CONCLUSIONS
  The prevalence of nickel allergy decreased among young female patients and increased among older female patients with dermatitis, probably because of a cohort effect. The overall prevalence of cobalt allergy increased from 1992 to 2009. No significant trend in the prevalence of nickel and cobalt allergy among male patients was found.
authors.affiliation: Department of Dermatology and Allergy Centre, Odense University Hospital, University of Southern Denmark, DK-5000 Odense C, Denmark.
authors.forename: Caroline
authors.initials: C
authors.lastname: Carøe
authors.forename: Klaus E
authors.initials: KE
authors.lastname: Andersen
authors.forename: Charlotte G
authors.initials: CG
authors.lastname: Mortz
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003035:Cobalt / Q000633:toxicity*; D003257:Consumer Product Safety / Q000331:legislation & jurisprudence*; D003718:Denmark / Q000453:epidemiology; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000453:epidemiology; D004485:Eczema / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009532:Nickel / Q000592:standards / Q000633:toxicity*; D010328:Patch Tests; D015995:Prevalence; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D003035:Cobalt; D009532:Nickel