Positive relationship-intensity of response to p-phenylenediamine on patch testing and cross-reactions with related allergens.
BACKGROUND
Hair dye exposure is the most common cause of sensitization to p-phenylenediamine (PPD). Cross-reactions with structurally related allergens occur.


OBJECTIVE
It is suggested that a stronger patch test reaction (3+ rather than 1+) to PPD (usually tested as 1% petrolatum) is associated with an increased propensity for cross-reactions. In this article we will demonstrate this association.


METHODS
Of 230 patients with allergic reactions to PPD on patch testing identified during 2007-2012 from clinical records, notes for 221 were available for review. Data were collected regarding age, sex, and grade of reaction [International Contact Dermatitis Research Group (ICDRG) criteria] to PPD. Cross-reactions with the following allergens, found in our baseline series, were recorded: Disperse Yellow 3, N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and caine mix. Having excluded 23 doubtful reactions, the reactions from 198 patients were further considered.


RESULTS
Of the patients, 75.3% (n = 149) were female, and the mean age was 48.6 years (12-82 years). Of the patients allergic to PPD, 16.6% (n = 33) showed cross-reactions with one or more related allergens. Cross-reactions were seen in 16% with a grade of 1+, 14.5% with a grade of 2+, 28.6% with a grade of 3+ when PPD was tested 1% pet., and 50.0% when PPD was tested at 0.1-0.001%, arbitrarily considered to be 4+ (p = 0.02; Cramér's V = 0.23).


CONCLUSIONS
An increasing likelihood of reactions to Disperse Yellow 3, IPPD or caine mix was seen with increasing strength of patch test reaction to PPD. The clinical relevance of these cross-reactions is unclear.
Department of Cutaneous Allergy, St John's Institute of Dermatology, London, SE1 7EH, UK.
Bjorn R
BR
Thomas
Ian R
IR
White
John P
JP
McFadden
Piu
P
Banerjee
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000779:Anesthetics, Local / Q000276:immunology*; D001391:Azo Compounds / Q000276:immunology*; D002648:Child; D003429:Cross Reactions; D017449:Dermatitis, Allergic Contact / Q000209:etiology / Q000276:immunology*; D005260:Female; D006202:Hair Dyes / Q000009:adverse effects / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests; D010655:Phenylenediamines / Q000276:immunology*; D012189:Retrospective Studies; D055815:Young Adult
D000779:Anesthetics, Local; D001391:Azo Compounds; D006202:Hair Dyes; D010655:Phenylenediamines; C024957:Dispersion Yellow 3; C014627:N-isopropyl-N-phenyl-4-phenylenediamine
PPD; contact allergy; cross-reactions; p-phenylenediamine; reaction strength