Influence of thermal hair straightening on cannabis and cocaine content in hair

Recent Periodical Literature:  by Viktor Naumovski

This article details an experiment that quantified and compared the concentrations of cannabis and cocaine in hair strands following thermal straightening. Past research has shown that treatments such as bleaching, dyeing and perming have the ability to lower the concentration of drugs being found within hair samples. Thermal straightening of hair has been examined and shown to cause radial and axial cracking as well as scale edge fusion due to examination under an electron microscope. This study focused on the effect thermal straightening would have on cocaine and THC content found in hair. To test this positive hair specimens were obtained, 17 positive for cannabis and 7 positive for cocaine, and samples were split into two groups so one could be treated in vitro with a curling iron. Samples were analyzed in triplicates by cleaning the hair samples then pulverizing them and performing a solid phase extraction, after which GC-MS was used to determine the concentrations of the positive hair samples.

From a comparison of the cannabis content in hair, there was a median decrease of 10.1%, while 11 of the 17 samples showed a decrease in THC content that ranged from 3% to 100%, while the remaining 6 cases showed an increase ranging from 4.6% to 67.2%. For CBN 15 samples (2 were negative originally) showed a significant increase after the straightening, with the ranges consisting of 72% to 751%.  Hair color also seemed to have an effect on the concentration of THC, as only darker hair had higher concentrations. The 7 samples of cocaine positive hair all showed a decrease, with the median being a decrease of 75.4%, from 44.6% to a complete loss of cocaine concentration. Concentrations of BZE were all found to be higher in the treated hair, ranging from 3.3 to 48.2% increase, which is a metabolite of cocaine so it suggests consumption occurred.  While the results of the THC levels weren’t completely as expected, overall hair straightening has to potential to cause faster metabolism of both cannabis and cocaine in hair and should be documented if it occurred prior to hair analysis, and people should be informed beforehand not to use a thermal straightener for the analysis to be considered accurate.

Ettlinger, Jana, and Michel Yegles. “Influence of Thermal Hair Straightening on Cannabis and Cocaine Content in Hair.” Forensic Science International 265 (2016): 13-16. Web. doi:10.1016/j.forsciint.2016.01.002  


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