A hair drug test is a specialized kind of drug test that attempts to determine the presence of certain classes of drugs in the hair samples of a subject. The hair sample used for conducting the test may be taken from the head or other body part, in some cases extracting the hair from beneath the skin.
A hair drug test can trace the history of substance (drug) abuse in a subject to as far back as six months. A number of points of criticism have been raised against hair drug tests, questioning their validity and social implications for certain ethnic groups. However, the procedure is increasingly being used in the US for various purposes.
Drug tests are performed to determine whether a certain drug, or any of its metabolized traces, exists in a body part or product of a person. A hair drug test is conducted to determine the presence (or absence) of a particular drug in the hair samples of a subject. The primary significance of a hair drug test lies in its high degree of accuracy; usually a typical hair drug test would trace the subject’s possible abuse of a particular drug to as far back as six months, especially for subjects who keep long hair.
This is because the suspected substance of abuse gets encased in the hair shaft and is preserved there, making it easier for the tester to detect it even months after its use.
The process of performing a hair drug test is fairly simple. Hair samples are taken from any part of the subject’s body, preferably from the head, and tested at a chemical laboratory for detecting the presence of different kinds of drugs including marijuana, cocaine, opiates (morphine, codeine etc.), and amphetamines (e.g. Ecstasy). It is not very useful for subjects to try to get a negative result by shaving their head because hair samples from other body parts also provide evidence of drug abuse. Further, in case hair is not available, hair follicles can be tested for a particular class of drug without affecting the accuracy of the test. This can be much more painful for the subject on account of the extraction of hair follicles out of the skin.
A hair drug test should always be performed at an accredited chemical laboratory, showing whether the drug exists (positive) in the hair or not (negative). The result also shows, in case of a positive result, whether the subject is an occasional or high-level user. Efficient laboratories usually provide the test’s result in two days after receiving the sample. It is important not to mix hair from different body parts in a single sample i.e. hair collected from head are not to be mixed with that from the body. Also, samples collected from hairbrush, or some other object of use, are not recommended for testing.
Conducting a hair drug test of prospective employees is a growing trend in the US despite the cons of hair drug testing. While advocates of hair drug test stress that the results are not affected significantly by usual treatments like shampooing or dying etc., some studies claim that hair washed with certain brands of shampoos show a significantly lower concentration of drugs.
Hair testing procedures have also been criticized for being racially biased, particularly against Africans. Further, hair tests may not prove sensitive for certain kinds of drugs, e.g. pot. Despite these points of criticism, the trend of using a hair drug test for determining a history of drug abuse is on a rise in the US.