Are cannabinoids detected in hair after washing with Cannabio shampoo?

Today, cannabis plants are used in shampoo preparations, in foodstuffs (e.g., oils, noodles, crackers, etc.), and in beverages (e.g., tea). These products often contain < 1% delta9-tetrahydrocannabinol (THC) in order to eliminate psychoactive effects, but some of them can include 1 to 3% of THC. Gas chromatography-mass spectrometry (GC-MS) analysis of Cannabio shampoo revealed the presence of THC (412 ng/mL) and two constituents of cannabis plants, cannabidiol (CBD, 4079 ng/mL) and cannabinol (CBN, 380 ng/mL). In order to verify if normal hygiene practices with Cannabio shampoo can result in positive tests for cannabinoids in hair, three subjects washed their hair with this shampoo once daily for two weeks. After this period, hair specimens were collected. In the three hair specimens, THC, CBD, and CBN were never detected within their limits of detection, 0.05, 0.02, and 0.01 ng/mg, respectively. We concluded that the use of Cannabio shampoo during normal hygiene practices cannot be considered as a source of potential contamination of hair. In a second experiment, drug-free hair specimens (200 mg) were incubated in 10 mL water/Cannabio shampoo (20:1, v/v) for 30 min, 2 h, and 5 h. After incubation, hair strands were washed with water and separated into two portions. One portion was extracted directly; the second was decontaminated with methylene chloride and then extracted. After an incubation period of 30 min, the analysis of hair by GC-MS did not reveal the presence of THC, CBD, and CBN in hair, regardless of whether the hair was decontaminated. After an incubation period of 2 h, specimens tested positive for CBD (0.11 ng/mg without decontamination and 0.10 ng/mg with decontamination) and CBN (0.02 ng/mg without decontamination and 0.02 ng/mg after decontamination). After an incubation period of 5 h, specimens tested positive for CBD (0.25 ng/mg without decontamination and 0.14 ng/mg after decontamination) and CBN (0.02 ng/mg without decontamination and 0.02 ng/mg after decontamination). In all cases, THC was never detected. Extensive but unrealistic use of Cannabio shampoo can cause drug-free hair to test positive for CBD and CBN but not for the primary psychoactive drug THC.