Hair analysis: Assessment of homemade hair treatment effects on drug concentrations in the keratin matrix

Hair is the matrix of choice for investigating a subject's drug history over time, usually with specific forensic applications (license renewal, workplace drug testing, toxicological evaluation), and it is generally considered difficult to be tampered with. Nevertheless, some treatments promising to lower drug concentrations in hair are described online as how to “pass” a drug test. We selected three of these practices, claiming to be effective in decreasing drug concentrations—Treatment 1: (A) baking soda, (B) salicylic acid, (C) bleach; Treatment 2: (A) bleaching and (B) dyeing; Treatment 3: (A) white vinegar, (B) salicylic acid moisturizer, (C) liquid cleanser, and (D) dyeing. Quantitative results were compared with those of untreated hair strands, used as reference. We evaluated the efficacy of the treatment on drugs of abuse and benzodiazepines. Treatment 1 proved to be the most effective, since drug concentrations in treated hair were significantly lower than in untreated ones, although methadone and tetrahydrocannabinol (THC) seemed to be less affected than cocaine and 6-monoacetylmorphine (MAM). The mean percentage values of treatment-induced decrease were up to 90% for cocaine, 81% for benzoylecgonine, 77% for morphine, 89% for MAM, 37% for methadone, 67% for ketamine, 80% for MDMA, 76% for methamphetamine, and 60% for THC, compared with the reference samples. There was no noticeable damage or discoloration of the keratin matrix, making it difficult for the technicians to determine if there was a treatment. This could be an issue for the application of cutoffs or when low concentrations of drugs are incorporated into the keratinic matrix.