title: Methylisothiazolinone Contact Allergy Prevalence in Western Canada: Increased Detection With 2000 ppm Patch Test Allergen.
abstract: BACKGROUND
  Contact allergy to methylisothiazolinone (MI) or to the combination of methylchloroisothiazolinone and MI (MCI/MI) is an important and increasing cause of allergic contact dermatitis, with prevalence rates higher than 10% in some centers.
  
  
  OBJECTIVE
  The objective of this retrospective chart review is to provide a western Canadian perspective on whether the positive patch testing rate to MCI/MI or MI increased during the testing period of 2008 to 2015 and whether the addition of MI at 2000 ppm resulted in increased detection.
  
  
  METHODS
  We conducted a retrospective chart review of patients who tested positive (n = 104) of 2177 total patients who were patch tested for MCI/MI or MI at a community dermatology clinic in Vancouver, British Columbia, Canada, from January 2008 through April 2015.
  
  
  RESULTS
  One hundred and four patients had positive patch testing results for MCI/MI, MI, or both. Positive results increased over the study period, with the highest prevalence in 2015 at 9.41% for MCI/MI, 12.94% for MI, and 15.29% for either. When testing for MI at 2000 ppm was introduced in 2013, the initial positive patch testing prevalence was 6.6%, followed by 10.1% in 2014, and 12.9% in 2015.
  
  
  CONCLUSIONS
  We demonstrate an increasing prevalence of MCI/MI and MI allergy between 2008 and 2015, with the highest prevalence of 15.29% in 2015 for MCI/MI and/or MI allergy. The addition of MI 2000 ppm greatly increased the positive patch testing yield for MI. Our results support the importance of continued efforts to monitor and regulate these preservatives.
authors.affiliation: 1 Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Wilford
authors.affiliation: 1 Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada.|2 Division of Dermatology, Department of Medicine, St. Paul's Hospital and Providence Health Care, Vancouver, BC, Canada.
authors.forename: Gillian C
authors.initials: GC
authors.lastname: de Gannes
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001955:British Columbia / Q000453:epidemiology; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000379:methods*; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013844:Thiazoles / Q000009:adverse effects*
chemical_list: D011310:Preservatives, Pharmaceutical; D013844:Thiazoles; C011506:2-methyl-4-isothiazolin-3-one; C011421:5-chloro-2-methyl-4-isothiazolin-3-one
keywords: allergy; contact; methylchloroisothiazolinone; methylisothiazolinone