Pierre Bore

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.

Evolution in the composition of human skin surface lipids during their accumulation on scalp and hair.

Qualitative examination of human surface lipids collected using a surfactant solution shows that there are no significant differences between individuals when the samples are collected after one day, starting from clean hair and scalp. On the contrary, samples collected after 4 days reveal discrepancies within the population, related to the oily hair symptom.

Differential thermal analysis of human sebum as a new approach to rheological behaviour

The oily aspect of a hair is not only the consequence of an excessive lipidic production on the scalp; the quality of the fatty mixture should also be considered.

Capillary gas chromatographic analysis of human skin surface lipids after microsampling on ground-glass platelets

Small amounts of human skin surface lipids, in the 1-20 micrograms range, sampled on ground-glass platelets are investigated using capillary gas chromatography. A first system allows the separation of the neutral lipids, up to the triglyceride fraction. A second system reveals the distribution of the free fatty acids or of the free + glyceride fatty acids, after a methylation or transesterification step. Examination of samples from nine subjects shows that the unsaturation of the free fatty acids increases during a four-day period of accumulation. Comparison of the free fatty acid fraction and the free + glyceride fatty acid fraction shows that the fraction is more saturated than the latter. It is concluded that the bacterial lipases which cleave the fatty acids from the ester bond favor the liberation of straight-chain saturated fatty acids from sebum triglycerides. This result is confirmed by comparison of the free fatty acid fraction with the glyceride fatty acid fraction separated from bulk samples of skin surface lipids from hair and scalp.

Human Hair Pigment: A Mild Isolation Procedure and a Method for Characterization

The first difficulty in beginning a study of hair pigment is to isolate the pigment from the keratin matrix without altering its chemical structure. Our isolation method differs from that of others in that we digest hair enzymatically.