title: Visual and confocal microscopic interpretation of patch tests to benzethonium chloride and benzalkonium chloride.
abstract: BACKGROUND
  Quaternary ammonium compounds (Quats), such as benzalkonium chloride (BAC) and benzethonium chloride (BEC), are widely used as antibacterial active ingredients and preservatives in personal care products, disinfectants, and ophthalmic preparations. BAC is known to be a marginal irritant when patch tested at 0.15% aq. Data on BEC are limited.
  
  
  OBJECTIVE
  To differentiate irritant from allergic patch test reactions to quaternary ammonium compounds.
  
  
  METHODS
  Eight subjects who were considered likely to react based on history of rash after exposure to disinfectants or a history of prior positive patch test to BAC were recruited, as well as two patients undergoing routine patch testing. BAC (0.15% aq), BAC (0.15% pet), BEC (0.05% aq), BEC (0.15% pet), BEC (0.15% aq), BEC (0.5% aq), sodium lauryl sulfate (2.0%), and deionized water were applied under Finn chambers for 48 h. Four days and 7 days after application, the sites were examined visually and then by in vivo reflectance confocal microscopy (RCM) which was interpreted by blinded experts.
  
  
  RESULTS
  Two patients with definite allergic reactions according to visual patch test reads and RCM were clinically relevant. Cross-reaction between BEC and BAC was demonstrated in one patient. RCM imaging correlated well with clinical scoring and interpretation of patch test reactions in terms of irritancy vs. allergy for BEC and BAC.
  
  
  CONCLUSIONS
  Relevant allergic reactions to quats occur in humans. Possible cross-reaction was noted to occur between BAC and BEC. RCM appears to be a useful tool in distinguishing between irritancy and sensitization during patch testing to BAC and BEC. Further study of prevalence and best test concentration and vehicle is needed.
authors.affiliation: Akron General Medical Center, Department of Medicine, Akron, OH 44307-2463, USA. bbohaty@neomed.edu
authors.forename: Bohaty
authors.initials: B
authors.lastname: Benjamin
authors.forename: Fricker
authors.initials: F
authors.lastname: Chris
authors.forename: González
authors.initials: G
authors.lastname: Salvador
authors.forename: Gill
authors.initials: G
authors.lastname: Melissa
authors.forename: Nedorost
authors.initials: N
authors.lastname: Susan
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents; D001548:Benzalkonium Compounds; D001558:Benzethonium; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis*; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods*; D015588:Observer Variation; D010328:Patch Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014796:Visual Perception / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D001548:Benzalkonium Compounds; D001558:Benzethonium