Background
The results from a previous study indicated the presence of several possible sensitizers formed during oxidation of the potent sensitizer p‐phenylenediamine (PPD) to which PPD‐sensitized patients might react, in various patterns.
Objectives
To extract and analyse a yellow spot from a thin‐layer chromatogram with oxidized PPD, to which 6 of 14 (43%) PPD‐positive patients had reacted in a previous study, in order to identify potential sensitizer(s) and to patch test this/these substance(s) in the 14 PPD‐positive patients.
Methods
The yellow spot was extracted from a thin‐layer chromatogram of oxidized PPD, and two substances, suspected to be allergens, were identified by analysis with gas chromatography mass spectrometry (GCMS). The 14 PPD‐positive patients, who had been previously tested with the thin‐layer chromatogram of oxidized PPD, participated in the investigation, and were tested with dilutions of the two substances.
Results
GCMS analysis identified 4‐nitroaniline and 4,4′‐azodianiline in the yellow spot. Of the 14 PPD‐positive test patients, 5 (36%) reacted to 4‐nitroaniline and 9 (64%) reacted to 4,4′‐azodianiline.
Conclusion
The results show that 4‐nitroaniline and 4,4′‐azodianiline, formed during oxidation of PPD, are potent sensitizers. PPD‐sensitized patients react to a high extent to concentrations equimolar to PPD of 4‐nitroaniline and 4,4′‐azodianiline.