title: Methylchloroisothiazolinone/Methylisothiazolinone and methylisothiazolinone allergy.
abstract: BACKGROUND
  Preservatives used in cosmetics tend to be, by their nature, allergenic. Methylisothiazolinone (MI) has been used as a sole preservative in multiple cosmetics, household goods, and toiletries. A current epidemic of MI has recently been reported in Europe.
  
  
  OBJECTIVE
  The aim of this study was to study the prevalence of methylchloroisothiazolinone/MI (MCI/MI) and MI allergy in a Bangkok dermatology clinic.
  
  
  METHODS
  During January 2009 to June 2014, 3253 consecutive patients tested with 100 ppm (0.01%) MCI/MI and patients tested with 2000 ppm (0.2%) MI were included in the study.
  
  
  RESULTS
  Three hundred twenty of 3253 patients (9.8%) tested for MCI/MI had a positive reaction. There was a steep increase in the prevalence of MCI/MI contact allergy from 4.8% in 2009 to 11.2% in 2011 and 17% in 2013. In the first 6 months of 2014, 22 of 54 cases tested for MI (40.7%) had a positive reaction. Among those who had a positive reaction to MI, 6 of 22 (27.3%) showed negative reaction to MCI/MI.
  
  
  CONCLUSIONS
  There is a similar prevalence of MI allergy in a Bangkok dermatology clinic as those reported in European centers such in the United Kingdom.
authors.affiliation: From the *Institute of Dermatology, Bangkok, Thailand; and †St John's Institute of Dermatology, London, United Kingdom.
authors.forename: Pailin
authors.initials: P
authors.lastname: Puangpet
authors.forename: Apawalee
authors.initials: A
authors.lastname: Chawarung
authors.forename: John P
authors.initials: JP
authors.lastname: McFadden
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000485:Allergens / Q000009:adverse effects*; D002648:Child; D015331:Cohort Studies; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects*; D015995:Prevalence; D013785:Thailand / Q000453:epidemiology; D013844:Thiazoles / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D000485:Allergens; D011310:Preservatives, Pharmaceutical; D013844:Thiazoles; C011506:2-methyl-4-isothiazolin-3-one; C011421:5-chloro-2-methyl-4-isothiazolin-3-one