Hair follicle testing typically tests for illegal recreational drugs, states Omega Laboratory. Some of the drugs that hair follicle testing can detect are marijuana, cocaine and popular opiates such as codeine and morphine.
In contrast to the more common urine testing, hair follicle testing uses hair from the head or the body and usually concludes in more positive illicit drug use findings explains Omega Laboratory. Hair analysis testing can detect drug use over a period of at least 90 days. It typically takes a drug five to 10 days to grow above the hair follicle, depending on the metabolism of the person being tested. Technicians usually perform this test on 1.5 inches of hair, starting from the shaft. This gives the ability to test for a time period of approximately 90 days, based on the average rate of 0.5 inch of monthly growth of hair on the human body.