How accurate is body hair compared to head hair analysis?

Those awaiting a drug test with hair will often be nervous - and for many, this worry can stem from the removal of hair itself. Will they be left with a bald patch? Is there enough head hair to get a decent sample?

It’s vital that your clients are adequately prepared for what to expect from a hair test, but in short: they won’t be left with a bald patch, and if there’s not enough head hair (or if it’s not suitable for testing, or they’ve attempted to “cheat” the hair test), we can test body hair instead.

When testing for evidence of drug or chronic excessive alcohol use, how accurate is body hair compared to head hair analysis?

There is no difference in accuracy

Body hair is just as accurate as head hair as a marker of drug or alcohol use. Both are collected and analysed in the same way. The accuracy of the end result is exactly the same. However, there is some difference in the result timeframes covered by each test type.

Head hair samples are more representative

While both head and body hair grow at a reasonably constant rate of 1 cm per month (with a range of 0.7 to 1.5 cm), the approximate time period covered by a head hair test is more representative of substance use when compared to an equivalent length of body hair.

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As a result of hair’s biology, only head hair can be cut into sections to produce a historical picture and pattern of drug use over monthly time frames. Hair exists in one of two phases - either resting or growing. In the resting phase, hair does not grow but still contains traces of substances from previous use.

Estimates show that 40-60% of body hair remains in the resting phase, compared with 10-15% of head hair. This means that a 3cm sample of body hair would represent a period of two to three times longer than a head hair of the same length, despite similar growth rates.

Choosing wisely

If you’re unsure whether to do a drug test with hair or body hair in your case, we’d advise discussing the matter with your laboratory. Different tests suit different scenarios.

If a hair test is ordered to cover a specific time period and both head and body hair are available, we would always recommend using head hair. Your client may have requested that hair is taken from the body rather than the head, but this is where we - and you - can reassure them that the sample collection site will not be visible.

If a hair test is ordered to cover a specific time period and head hair is not available - for example, if the donor is bald, if they have alopecia and are worried about losing more hair, or if they have bleached their hair so significantly that it may impact on test results - then body hair should be used.

If sectional analysis is required to demonstrate that an individual has changed their use of drugs - in a workplace rehabilitation programme, for example, or to prove to a court that they are fit to retain or regain custody of a child - head hair should be used. Sectional analysis of body hair is not possible.

A key part of the value of hair testing is its versatility. When a sample of head hair isn’t possible, body hair can be used instead. When this happens, however, it’s important to understand how the detection timeframe for the sample is affected. This might make an important difference to the case outcome.

Whatever your clients’ situation, it’s vital to work with a testing laboratory that will listen to your requirements and advise you of the best method for your situation. For further information, or for answers to any of your questions on drug or alcohol hair strand testing, call us on 02920 682031 or email info@cansfordlabs.co.uk.