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Study: Hair Tests Less Likely To Detect Cannabinoids Following Cosmetic Treatments

Thursday, 14 March 2019

Marijuana Hair Testing

Dudelange, Luxembourg: Cosmetic hair treatments, such as bleaching or perming, interfere with the detection of cannabinoids and their metabolites in hair, according to data published in the journal Forensic Science International.

A pair of European researchers assessed the impact of various cosmetic treatments -- including bleaching, perming, and dyeing -- on 30 THC-positive hair samples.

They concluded: "We found that any type of cosmetic hair treatment has an effect on cannabinoid concentrations in hair. ... Bleaching and perming reduced all cannabinoids concentration in hair; THC was more affected than THC-COOH [the carboxy-THC metabolite], CBN [cannabinol] and CBD [cannabidol]. Bleaching caused strong chemical degradation on cannabinoids, while perming exerted more a leaching out effect. Permanent colorings in single applications had only little effects on cannabinoids."

Prior studies of hair follicle drug detection testing have reported that the tests are far more likely to identify those who engage in the daily use of cannabis as compared to those who consume it only occasionally.

For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, "Influence of cosmetic hair treatments on cannabinoids in hair; bleaching, perming, and permanent coloring," appears in Forensic Science International.