Hair Follicle Drug Testing 101

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5 September 2023

Hair Follicle Drug Testing 101

As employers consider how to ensure a safe and healthy workplace, they often decide to do some type of drug testing, especially with new hires. While urine screening is the most common method to determine if someone has used an illegal substance, it has a short window time in relation to when it can detect past drug use. Because an applicant is told about the testing, they can sometimes abstain from drug use long enough prior to providing a urine sample to test clean. (Note: This may not prevent marijuana from being detected, but it also can’t prove any pattern of use.)

A more accurate way of determining a history of drug use is to test a follicle, or strand, of hair. This simple method does not violate privacy in legal terms. It also can detect drug use during the previous 90 days. (Learn more in "Oral Fluid, Urine, and Hair Testing: What's the Difference?")

How does hair follicle testing work?

Hair follicle testing is quite simple. A hair specimen, usually from the head, is collected, labeled, and sent to an accredited laboratory. At the lab, the hair is washed to remove any contaminants. Agencies who do the testing must follow stringent FDA guidelines regarding washing and testing the hair.

How much hair is needed?

Hair grows about ½ inch per month. For accuracy over the past 90 days, 100-120 strands of hair (about the size of a pencil eraser) are taken 1½ inches away from the scalp. If body hair is used, the time frame may be longer, because of different hair growth rates. Body hair can show use up to one year prior to collecting the sample, and is considered less accurate.

How recent can drug use be detected?

About 5-10 days after drug use, new hair reaches the scalp, where it can be collected and tested.

Free Download: An In-Depth Look at Drug Hair Testing

Which drugs can be identified?

A 5-panel hair test detects cocaine, marijuana, phencyclidine (PCP), opiates (including codeine, morphine, and 6-acetylmorphine), and amphetamines (including amphetamine, methamphetamine, MDMA, and MDA). (Learn more in "Drug Abbreviations Used in Drug Testing".) If the employer wishes, the opiate screening can be extended to look for oxycodone, oxymorphone, hydrocodone, and hydromorphone. (Learn more in "A Look at Prescription Drug Abuse Statistics".)

How long does it take to get results?

Depending on the lab’s test run schedule, negative results can be reported in as little as one day. If a specimen returns an initial positive result, confirmatory testing takes 2-3 more days.

How accurate is hair follicle testing?

Two independent studies reported that hair testing revealed 4-8 times more drug users than with urine testing. The technique involves the standard Enzyme-Linked-Immunosorbent Assay (ELISA) methodology. Samples that seem positive undergo confirmatory testing by using a combination of gas chromatography, mass spectrometry, or liquid chromatography.

How are the cut-off levels determined?

Cut-off levels are the same industry-wide. They are similar to those in the 2004 guidelines proposed by the Substance Abuse and Mental Health Services Administration (SAMHSA). (Learn more in "Drug Detection Cutoffs: What You Need to Know".)

What about the legality of hair follicle testing?

Courts have upheld the validity and reliability of hair testing. As with all sample collections, the legal chain-of-custody procedure must be followed. The Federal guidelines have been established by SAMHSA and the College of American Pathologists. Samples must be safely stored for at least one year and test results are kept for two years, or as state law dictates.

Are there situations when hair follicle testing is not appropriate?

Hair follicle testing is not recommended for either post-accident or reasonable suspicion testing. This is because those results need to indicate recent use. Since hair shows a 90-day use window, it cannot narrow down drug use to the relevant time frame. (Learn more in "8 Things Employers Should Know About DOT Drug and Alcohol Testing".)

How much does hair follicle testing cost?

The average cost is currently about $200, more than a simple urine screen. However, many employers prefer to invest in a drug test that shows a long-term history, because of potential expenses involved with reduced productivity, absenteeism, and treatment.

Is it possible to cheat on a hair follicle test?

The Internet abounds with advice on how to beat the test with shampoos and rinses. However, most people agree that it’s much more difficult than cheating on a urine screen, with uncertain results. (Learn more in "How to Avoid Adulteration in Employee Drug Testing".) Also, the sample is obtained by a professional and immediately labeled; there is no opportunity for tampering or substitution. According to one DNA legal specialist firm, bleached hair can damage the hair shafts, affecting the outcome. A forensic lab recommends not testing hair that has been permed, colored, or straightened.

Does my state permit hair follicle testing?

Every state allows for urine drug screening. Other allowed testing methods vary by state. Some states (and federal DOT regulations) may require urine testing, even if another method is used. (Learn more in "DOT vs. Non DOT Testing: What's the Difference?")

Should my company use hair follicle testing?

Whether or not a company should use hair follicle drug testing depends on several factors. Some industries, such as trucking, find it particularly worthwhile. Each company should review its policies, job risks, and expenses related to lost work time. Obtain legal counsel regarding Federal, state, and local laws before implementing new drug screening methods. (Learn more in "State Drug Testing Laws: What Should Employers Know?")