title: Contact sensitization to methylisothiazolinone in Finland--a multicentre study.
abstract: BACKGROUND
  Antimicrobials constitute the second most common cause of contact allergy to cosmetics. Methylisothiazolinone (MI), previously always used together with methylchloroisothiazolinone (MCI), has recently been approved in the EU for use on its own in cosmetics and also various industrial products. MCI has been classified as an extreme-strong and MI as a strong-moderate sensitizer.
  
  
  OBJECTIVE
  To study the frequency of positive patch test reactions to MI, and its relevance and relation to MCI/MI sensitivity, in Finland.
  
  
  METHODS
  Over a period of 3 years (2006-2008), MI 0.1% (1000 ppm) and 0.03% (300 ppm) were patch tested in 10,821 patients at eight Finnish dermatological clinics. During 2008, patients with positive reactions to MI were asked to take part in a repeated open application test (ROAT).
  
  
  RESULTS
  Of the patients tested, 1.4% and 0.6% showed positive patch test reactions to 0.1% and 0.03% MI, respectively. Sixty-six per cent of those who were MI-positive were also positive to 100 ppm MCI/MI. Thirty-three agreed to undergo the use test, and 10 of these gave positive results (30%).
  
  
  CONCLUSIONS
  Our data show that MI used alone also potentially induces contact allergy. Careful monitoring is needed to determine whether or not this antimicrobial is safe to use in cosmetics.
authors.affiliation: Department of Dermatology, Skin and Allergy Hospital, Helsinki University Central Hospital, FIN-00250 Helsinki, Finland. leena.ackermann@hus.fi
authors.forename: Leena
authors.initials: L
authors.lastname: Ackermann
authors.forename: Kristiina
authors.initials: K
authors.lastname: Aalto-Korte
authors.forename: Kristiina
authors.initials: K
authors.lastname: Alanko
authors.forename: Taina
authors.initials: T
authors.lastname: Hasan
authors.forename: Riitta
authors.initials: R
authors.lastname: Jolanki
authors.forename: Kaija
authors.initials: K
authors.lastname: Lammintausta
authors.forename: Antti
authors.initials: A
authors.lastname: Lauerma
authors.forename: Arja
authors.initials: A
authors.lastname: Laukkanen
authors.forename: Jussi
authors.initials: J
authors.lastname: Liippo
authors.forename: Riitta
authors.initials: R
authors.lastname: Riekki
authors.forename: Anna-Maija
authors.initials: AM
authors.lastname: Vuorela
authors.forename: Tapio
authors.initials: T
authors.lastname: Rantanen
mesh_terms: D003358:Cosmetics / Q000737:chemistry*; D017449:Dermatitis, Allergic Contact / Q000209:etiology*; D005387:Finland; D006801:Humans; D010328:Patch Tests; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects*; D013844:Thiazoles / Q000009:adverse effects*
chemical_list: D003358:Cosmetics; D011310:Preservatives, Pharmaceutical; D013844:Thiazoles; C011506:2-methyl-4-isothiazolin-3-one; C011421:5-chloro-2-methyl-4-isothiazolin-3-one