3-[[2-(acetyloxy)ethyl][4-[(4-nitrophenyl)azo]phenyl]amino]propiononitrile

Non flammable

The synthetic azo dye Disperse Orange 31 was wrongly substituted by Disperse Orange 3 in patch test materials from Chemotechnique. This situation explains why a relatively low percentage of patients positive to PPD were positive to Disperse Orange 3, although a coreaction is explained to be very frequent because of skin transformation of Disperse Orange 3 into PPD.