By: Jenna Bouley,

Hair-follicle drug testing is different than other drug tests administered because it analyzes hair for drugs within the hair shaft, rather than bodily fluids normally used for drug testing such as urine or saliva.[1] Hair-follicle drug tests are particularly useful because they can be used to determine if a person has ingested drugs in the past 90 days.[2] Employers find this method useful because hair tests can identify drugs in someone’s system from approximately the last three months whereas urine tests can only detect drugs taken approximately a week prior to testing.[3] The use of hair-follicle drug testing has also become more common in the legal industry particularly when court-ordered drug testing may be required.[4] Some examples of when a hair-follicle drug test may be used for legal purposes include: probation, divorce, and child custody cases.[5]

Although the test is called a hair follicle test, it is not actually the root itself that is tested but the first inch and a half of growth from the base.[6] The test works to detect drugs taken in the last 90 days because when a person ingests a drug, it enters into the bloodstream while the body simultaneously metabolizes the drug, causing those metabolites to circulate through the blood as well.[7] Moreover because a person’s blood nourishes their hair follicles, any ingested drugs and their metabolites are deposited into their hair follicle where they remains until the hair grows out of the follicle.[8]

While on the surface hair-follicle drug testing may seem like a great solution for employers and courts there are some issues with the testing. Two major issues include the fact that someone could be exposed to a drug without having ingested it and therefore test positive as well as the fact that the drugs bond with some hair types better than others, which cause inaccuracies about when a drug might have been taken.[9] Some scientists argue that both external and ingested cocaine binds to melanin in the hair thus someone could potentially test positive for cocaine use simply by being in an environment that has cocaine.[10] Moreover, people with black hair, especially with the subtype eumelanin, tend to bind particularly well with cocaine and amphetamines causing disparities in timing between them and their lighter haired counterparts.[11] Additionally, both the amount of melanin and chemical treatment in someone’s hair can make a difference in how much of a drug the hair can absorb.[12] However, even with these issues employers still seem willing to use this method of drug testing.[13]

One example of how the courts have dealt with the issues presented by hair-follicle drug testing was a Massachusetts case involving Boston police officers who tested positive for cocaine in a hair-follicle test.[14] The court concluded that, although hair-follicle drug tests are reliable enough to “be used as some evidence” of drug use, “the risk of a false positive test was great enough to require additional evidence to terminate an officer for just cause.”[15] In other words, the officers failure to pass the hair-follicle drug testing could not be used to conclusively determine that they had used a controlled substance. As a result of the court’s decision the some of the officers were reinstated.[16] In support of the conclusion that this type of testing may be unreliable, Lewis Maltby, president and founder of the National Workrights Institute commented that “every independent scientific organization that has studied hair testing concluded that it isn’t reliable,” and that “the only scientists that support hair testing have ties to the industry.”[17] Moreover according to Michael Walsh, who designed the federal employee drug-testing regime under President Ronald Reagan, and was the executive director of President George H.W. Bush’s Drug Advisory Council: “the science basically just didn’t support integrating it into the federal program—there are still significant scientific issues, not about whether the technology can detect drugs in hair, but more so about the interpretation of how the drugs got there.”[18] Until a better method is found this issue will continue to present employers with the choice of using the potentially problematic hair-follicle drug testing and risk having a law suit brought or alternatively taking the chance that their employees may have used drugs within the last 90 days.


[1] See Hair Drug Test Facts and FAQS, Pyschemedics Corp., (last visited Apr. 9. 2018).

[2] See Hair Follicle Drug Test, National Drug Screening, Inc. (last visited Apr. 9. 2018).

[3] See id.

[4] See id.

[5] See id.

[6] See id.

[7] Supra note 2.

[8] See id.

[9]  See Ellen Airhart, The Hairy Problem with Drug Testing, Wired (Apr. 1, 2018, 8:00 AM)

[10] See id.

[11] See id.

[12] See id.

[13] See id.

[14] See Hassan Kanu, Hair-Follicle Drug Testing: Lessons for Employers, Bloomberg Law (Oct. 19 2016)

[15] Id.

[16] See id.

[17] Id.

[18] Id.

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