Hair testing is the most accurate and effective method of finding
users of drug abuse. Using a small sample of hair cut from the scalp,
hair analysis evaluates the number of drug metabolites embedded
inside the hair shaft.
When compared to more traditional forms of testing (i.e, urine testing), hair samples can detect a longer period of drug use. With urine, most drugs are undetectable if urinalysis is carried out more than 2-3 days after use, with the exception of cannabis, which may be detected for slightly longer periods of time.
After the 2-3 day period, a urine donor will test negative and slip through the urine screening process. With hair samples, the only time limitation for detecting drug usage is imposed by the length of the donor's hair. Every half inch of head hair in length provides a 30-day history of drug use.
The standard for the industry is to test 1.5 inches, which provides a 90-day history of the donor's drug use. If no head hair is available, body hair can
This provides longer window of detection of approximately 365 days.
Bleaches, shampoos and external contaminants (i.e. cannabis smoke) have no known impact on the results.