Many drug tests are carried out by means of hair analysis. The aim of the present study was to clarify if and to what extent it is possible to manipulate the results of hair analyses on tetrahydrocannabinol (THC) by using various commercially available everyday products and products advertised on the internet to be able to reduce the concentrations of drugs in hair. Fifty-four THC-positive hair samples were analyzed using liquid chromatography tandem mass spectrometry; they were analyzed untreated or treated with Vodka Gorbatschow® (n = 19), Seborin® hair tonic (n = 11), Zydot® shampoo (n = 6), Desderman® disinfectant (n = 11) and Head and Shoulders® shampoo (n = 7). A mean reduction of 52% (Zydot® shampoo) to 65% (Desderman®) was shown. Hair treatments could not be detected visually. Hair concentrations could also be decreased to non-detectability by using these everyday hair care products. Therefore, it is recommended to complement abstinence controls using hair samples by urine analysis and to not over-interpret quantitative results of THC concentrations in hair.
Keywords: bleaching; coloring; drug screening; forensics; hair; hair care products; manipulation; tetrahydrocannabinol.