A major challenge in hair analysis is external contamination, which occurs when drug residues from environmental exposure or direct contact with substances like cocaine or cannabis are deposited onto the hair.
Initially hair analysis focused on a limited number of substances (e.g. opiates, cocaine and later with cannabis). With the introduction of high-resolution techniques in the routine, hair testing now includes a wider array of drugs, including alcohol markers (ethyl-glucuronide), or new ...