title: Patch test reactivity to metal allergens following regulatory interventions: a 33-year retrospective study.
abstract: BACKGROUND
  Contact allergy epidemics to chromate and nickel were addressed in Denmark in 1983 and 1990 by regulatory interventions.
  
  
  OBJECTIVE
  To evaluate whether regulatory interventions on nickel and chromate exposure have reduced the proportion of strong patch test reactions.
  
  
  METHODS
  22 506 patients with dermatitis aged 4-99 years were patch tested with nickel sulfate, potassium dichromate, or cobalt chloride between 1977 and 2009.
  
  
  RESULTS
  The proportion of 3+ reactions to nickel sulfate was reduced and almost disappeared after the mid- and late 1980s (P-trend = 0.001). Today, 1+ and 2+ nickel reactions occur equally frequent. Cobalt chloride patch test reactivity reflected the nickel development to some degree. The proportion of 3+ reactions to potassium dichromate was reduced during the 1980s (P-trend = 0.13), whereas the proportion of 2+ reactions to potassium dichromate have increased in recent years.
  
  
  CONCLUSIONS
  The decrease in nickel sulfate and cobalt chloride 3+ patch test reactivity began long before the Danish nickel regulation came into effect. This could be because of research activity at the time as well as political attention in Northern Europe. The chromate content in cement regulation may have changed the epidemiology of patch test reactivity; however, in recent years, 2+ reactions to chromate have increased markedly, a development that should be carefully followed.
authors.affiliation: National Allergy Research Centre, Department of Dermato-Allergology, Copenhagen University Hospital Gentofte, University of Copenhagen, DK-2900 Hellerup, Denmark. jacpth01@geh.regionh.dk
authors.forename: Jacob Pontoppidan
authors.initials: JP
authors.lastname: Thyssen
authors.forename: Katrine
authors.initials: K
authors.lastname: Ross-Hansen
authors.forename: Torkil
authors.initials: T
authors.lastname: Menné
authors.forename: Jeanne Duus
authors.initials: JD
authors.lastname: Johansen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000485:Allergens / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D003035:Cobalt / Q000009:adverse effects* / Q000592:standards; D003718:Denmark / Q000453:epidemiology; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000453:epidemiology*; D004781:Environmental Exposure / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009532:Nickel / Q000009:adverse effects* / Q000592:standards; D010328:Patch Tests; D011192:Potassium Dichromate / Q000009:adverse effects* / Q000592:standards; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D000485:Allergens; D003035:Cobalt; C029938:nickel sulfate; D009532:Nickel; C018021:cobaltous chloride; D011192:Potassium Dichromate