Several methods for drug testing exist, including urinalysis, oral swab, sweat patch and hair follicle testing. A hair test studies as many as 100 strands of hair taken from near your scalp. The examiner tests the shafts of the hair for traces of any drug you have ingested or the materials created when your body metabolises the drug. While advantages of hair follicle testing exist, it does have some drawbacks.
An advantage of hair testing is that drug use is detectable for months after ingestion. Hair grows at an average of just under one-half inch per month, so a one and one-half inch strand of hair holds signs of any drugs used within the previous three months. A disadvantage of this method is the time it takes for the drug to show up within the shaft. Because of the growth rate, hair follicle testing is not recommended for determination of recent drug use. It may be up to a week before the hair has grown out enough to hold traces of the drug. It can also take longer to get the results of the test, as the sample must go to a lab for analysis.
Hair follicle testing is a convenient method because it is noninvasive and less embarrassing for the subject than urinalysis. The sample is easy to collect and transport to the lab. No refrigeration is required to "keep" the sample until testing. As long as a trusted representative is collecting the strands, it is difficult for the subject to alter the sample. Hair samples also will not deteriorate, making collection an overall positive aspect of this method.
The substances detectable in hair follicle testing include amphetamines, methamphetamines, ecstasy, cocaine and opiates. This method can detect marijuana use, but is not considered as effective as urinalysis, due in part to the possible exposure by second-hand smoke. The window of detection, however, makes hair testing useful in monitoring chronic drug use. Sections of hair without traces of drugs represent a period free of substance use, important information if the subject is under legal or other supervision. Another disadvantage is the inability to test solely for alcohol use.
Hair follicle drug testing is a highly accurate method and is widely accepted in court cases. A drawback is the higher expense compared to other methods of testing. An obvious disadvantage is if the subject does not have any hair on his head. This can sometimes be handled using other body hair, provided it is long enough.