Percutaneous absorption of p-phenylene diamine during an actual hair dyeing procedure

An analytical method has been developed that allows the determination of p-phenylene diamine derivatives in urinary samples collected from women after hair dyeing with commercial formulations. During an on-line flash hydrolysis of the urine, a number of metabolites of p-phenylene diamine were hydrolyzed to free p-phenylene diamine, which was then determined using gas chromatography-mass spectrometry. The excretion of metabolites of p-phenylene diamine could be followed during 24 or 48 hours after the dye had been applied. Most of the p-phenylene diamine cleaved by the flash hydrolysis procedure was, in fact, involved in the N,N'-diacetyl combination. The dose excretion for p-phenylene diamine as measured by this method was comparable to that found by other authors who made use of radioactively labelled material. The present analytical method can be used to evaluate procedures intended to decrease the percutaneous absorption of p-phenylene diamine. Thus, a five- to ten-fold decrease in its penetration was observed by protecting the scalp with clay before applying the dyeing composition.