title: Is the irritant benzalkonium chloride a contact allergen? A contribution to the ongoing debate from a clinical perspective.
abstract: BACKGROUND
  Benzalkonium chloride (BAC) is a well-recognized irritant. However, doubts exist that it is also a contact allergen.
  
  
  OBJECTIVE
  Analysis of clinical patch test data addressing the reaction profile and synchronous reproducibility of BAC 0.1% in petrolatum (pet.) and possible increases in risk of BAC contact allergy in certain (occupationally exposed) subgroups. PATIENTS /METHODS: Data of 42 898 patients tested with BAC 0.1% in pet. in 3 different series (topical drugs, ophthalmics, and disinfectants) in the departments of the Information Network of Departments of Dermatology (http://www.ivdk.org) between 1996 and 2006 was analysed.
  
  
  RESULTS
  Overall, morphologically 'positive' reactions were rare, 0.6-1.5%, with a total of 41 stronger positive reactions. Concordance, assessed in 3322 patients tested in duplicate, was low (kappa coefficient 0.15, 95% CI: 0-0.31). Positive test reactions were observed significantly more often in the disinfectants series compared with the 2 other series, indicating that suspected exposure to disinfectants may be associated with sensitization. However, variation of stronger BAC test positivity across potentially relevant (occupational) groups was non-significant.
  
  
  CONCLUSIONS
  This analysis of routine clinical data and a number of previous reports add further, if weak, evidence to the notion that BAC is a contact allergen, albeit a very rare one.
authors.affiliation: Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen-Nürnberg, D-91054 Erlangen, Germany. wolfgang.uter@rzmail.uni-erlangen.de
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Uter
authors.forename: Holger
authors.initials: H
authors.lastname: Lessmann
authors.forename: Johannes
authors.initials: J
authors.lastname: Geier
authors.forename: Axel
authors.initials: A
authors.lastname: Schnuch
mesh_terms: D000328:Adult; D000368:Aged; D000485:Allergens / Q000009:adverse effects*; D001548:Benzalkonium Compounds / Q000009:adverse effects*; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D017453:Dermatitis, Irritant / Q000175:diagnosis / Q000209:etiology; D004202:Disinfectants / Q000009:adverse effects*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects; D010328:Patch Tests; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects*; D015995:Prevalence; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D000485:Allergens; D001548:Benzalkonium Compounds; D004202:Disinfectants; D011310:Preservatives, Pharmaceutical