title: Assessment of the elicitation response in subjects weakly sensitized to p-phenylenediamine.
abstract: BACKGROUND
  A 30-min application of a hair dye product containing 2% p-phenylenediamine (PPD) to subjects diagnostically graded +, showed that 12 of 18 reacted; eight of 18 with a true + and four of 18 with a doubtful (?+) response, whereas six of 18 did not react at all. In vitro skin-binding experiments showed that for diagnostic patch test conditions the measured exposure level (MEL) is more than 10-fold higher than the MEL for hair dyeing conditions.
  
  
  OBJECTIVE
  To further analyse the limited elicitation response of the diagnostically + graded subjects to a PPD hair dye product, under standardized test conditions mimicking product usage, by varying exposure time and dose.
  
  
  METHODS
  A hair dye model formulation containing 2% PPD, applied for 30, 45 and 60 min and a diagnostic PPD TRUE test(®) were applied to assess elicitation responses to increasing PPD exposure levels. Grading was performed according to International Contact Dermatitis Research Group guidelines.
  
  
  RESULTS
  Six subjects were available for this follow-up study. One of six subjects responded with a + elicitation response to the hair dye model applied for 60 min. Four of the five remaining subjects elicited a + response to the PPD TRUE test(®) applied subsequently, while one of five responded doubtfully.
  
  
  CONCLUSIONS
  Increasing the PPD exposure time twofold--resulting in a 5-6% increase of sensitivity of this hair dye model test--or further extending the exposure time 48-fold, was found sufficient to increase the MEL above the thresholds needed to elicit individuals with a + diagnostic PPD patch test who did not react to typical hair dye use conditions with a MEL of about 6·8 μg cm⁻². This analysis confirms that consideration of the MEL is a useful tool to better characterize thresholds of elicitation than consideration of the applied dose alone.
authors.affiliation: Department of Dermatology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
authors.forename: L M
authors.initials: LM
authors.lastname: Pot
authors.forename: P J
authors.initials: PJ
authors.lastname: Coenraads
authors.forename: C
authors.initials: C
authors.lastname: Goebel
authors.forename: B
authors.initials: B
authors.lastname: Blömeke
mesh_terms: D000328:Adult; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis* / Q000209:etiology; D004342:Drug Hypersensitivity / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006202:Hair Dyes / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D010328:Patch Tests / Q000379:methods; D010655:Phenylenediamines / Q000009:adverse effects*; D013997:Time Factors; D055815:Young Adult
chemical_list: D006202:Hair Dyes; D010655:Phenylenediamines; C029728:4-phenylenediamine