Poole, United Kingdom: The application of commercially available hemp seed oil products to hair can result in a positive test result for cannabinoids on a hair follicle drug detection test, according to data published in the journal Scientific Reports.
British researchers performed hair follicle drug detection tests on a group of ten volunteers who had applied commercially available hemp seed oil to their hair for a period of six weeks. The product utilized in the study did not contain detectable levels of THC. Prior to participating in the trial, all volunteers declared that they had not ingested cannabis in any form, nor had they been exposed to cannabis (smoke or otherwise) in any form via passive exposure.
Investigators reported, "Application of hemp oil to hair resulted in the incorporation of one or more cannabis constituents in 89 percent of volunteers, and 33 percent of the group tested positive for the three major constituents, THC, CBN [cannabinol] and CBD [cannabidiol]."
They concluded, "It is of concern that cannabinoids have been detected in hair samples following the application of hemp oil as a cosmetic procedure, and at levels in our study relevant to suggest cannabis exposure in some cases. ... We suggest that cosmetic use of hemp oil should be recorded when sampling head hair for analysis, and that the interpretative value of cannabinoid hair measurements from people reporting application of hemp oil is treated with caution in both criminology and public health."
Full text of the study, "Detection of cannabinoids in hair after cosmetic application of hemp oil," appears online in the journal Scientific Reports.