title: Patch testing with serial dilutions of various isothiazolinones in patients hypersensitive to methylchloroisothiazolinone/methylisothiazolinone.
abstract: BACKGROUND
  In 2005, methylisothiazolinone (MI) on its own came into use as a preservative. Prior to that, MI was always present together with methylchloroisothiazolinone (MCI). Can the pattern of reactivity to the separate active ingredients in allergic patients tell us something about the primary sensitizer?
  
  
  OBJECTIVE
  To investigate the potential pattern of cross-reactivity between the isothiazolinones tested, and to find the minimal elicitation concentration for each chemical, in order to determine whether the primary sensitizer is MCI or MI.
  
  
  METHODS
  Patients reacting to MCI/MI and/or MI were additionally patch tested with MCI/MI, MCI, MI, 2-n-octyl-4-isothiazolin-3-one (OIT) and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (dichloro-OIT) in serial dilutions.
  
  
  RESULTS
  Three different groups of reactors were seen. One group did not react to MI; another group reacted to both MCI and MI, but had higher patch test reactivity to MCI; and a third group reacted to both MCI and MI with very similar patch test reactivity, but reacted more often to OIT and dichloro-OIT.
  
  
  CONCLUSIONS
  Patch testing with the active ingredients of MCI/MI in serial dilutions could give information on the primary sensitizer.
authors.affiliation: Department of Occupational and Environmental Dermatology, Skåne University Hospital, Lund University, SE-205 02 Malmö, Sweden.
authors.forename: Marléne
authors.initials: M
authors.lastname: Isaksson
authors.forename: Birgitta
authors.initials: B
authors.lastname: Gruvberger
authors.forename: Magnus
authors.initials: M
authors.lastname: Bruze
mesh_terms: D003358:Cosmetics / Q000009:adverse effects / Q000737:chemistry; D003429:Cross Reactions; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis* / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000379:methods*; D011310:Preservatives, Pharmaceutical / Q000008:administration & dosage* / Q000009:adverse effects; D013844:Thiazoles / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
chemical_list: D003358:Cosmetics; D011310:Preservatives, Pharmaceutical; D013844:Thiazoles; C059792:4,5-dichloro-2-methyl-4-isothiazolin-3-one; C011506:2-methyl-4-isothiazolin-3-one; C035331:2-n-octyl-4-isothiazolin-3-one; C011421:5-chloro-2-methyl-4-isothiazolin-3-one
keywords: 2-n-octyl-4-isothiazolin-3-one (OIT) CAS no. 26530-20-1; 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (dichloro- OIT) CAS no. 64359-81-5; contact allergy, patch testing, methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) 3:1 CAS no. 55965-84-9; cross-reactivity; methylchloroisothiazolinone MCI CAS no. 26172-55-4; methylisothiazolinone (MI) CAS no. 2682-20-4