Hair Drug Testing
The technology capitalises on the way the body metabolises ingested drugs as they flow through the blood stream and deposit in the cortex of the hair. Hair is stable and the deposits are permanently embedded in the hair, so hair acts like a tape recorder — “recording” drug deposits in proportion to the use over time.
Hair testing analyses for drugs within the hair shaft, rather than body fluids like urine or saliva, to determine whether drugs of abuse are present. Compared to analysis of body fluids, hair testing is highly resistant to evasion by adulterating or substituting samples, or by simply abstaining from drug use for a few days.
Unlike urine drug testing, which may only detect drug use within the past 2-3 days, hair testing is able to detect a pattern of repetitive drug use for up to 90 days. A hair test is the most effective way to evaluate long-term patterns of use, making it an excellent option for a pre-employment or random testing programs and child custody cases.
It is important to note that, due to the relatively slow growth of hair, a single use of drug will not typically be detected during a hair analysis.
Rather, hair testing is best used to answer the question "Did the subject chronically use a drug within the past X months?" (where X is related to the length of the hair).
It does not answer the questions "Has the subject ever used this drug?" or "Did the subject use this drug on any occasion within the past X months?”