On cosmetically treated hair--aspects and pitfalls of interpretation.

Popular hair cosmetic treatments like bleaching or permanent waving were found to affect the stability of incorporated drugs and to cause alterations of the fibers at an ultrastructural level. This may result in a partial or complete loss of drug substances, depending on the particular drug molecule and on its concentration prior to the cosmetic treatment. Moreover, from literature, there is some evidence that drug molecules are not only incorporated into the growing fiber by passive diffusion from blood into the matrix cells and melanocytes, but that the substances enter the hair also via perspiration such as sweat and sebum. Since permed and bleached hair shows an enhanced sorption capacity, the risk of false positives or an unusually high drug concentration in cosmetically treated hair was under investigation. Virgin, permed, mildly as well as severely bleached tresses were exposed to artificial sweat or sebum containing cocaine, benzoylecgonine, 6-acetylmorphine, morphine and codeine (500 ng/g). Except codeine, the concentrations measured by GC/MS were very small and quite close to the detection limit indicating a minor importance of drug uptake into hair fiber from the endogenous-exogenous shunt via sebum or sweat. From the results it is concluded that an increased risk of false positive results in hair analysis on bleached and permanent waved hair fibers does exist, but is not particularly severe.