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What affects a hair drug test result?
There are many factors that have the potential to impact the results of a hair drug test, including:
- Hair treatments, such as bleaching, dyeing, perming and straightening
- Hair colour
- Hair growth rate and length of hair available
- Environmental factors, such as passive exposure to drugs
- Attempting to ‘cheat’ the test
Here, we explore hair drug testing in more detail, including how it works and the external factors that could affect a hair drug test result.
- What is hair drug testing?
- How does head hair drug testing work?
- How does body hair drug testing work?
- How are hair samples collected and tested for hair drug testing?
- What affects hair drug test results?
- What factors are considered when compiling a hair drug test report?
- What’s included in an AlphaBiolabs hair drug test report?
- Where can I get a hair drug test?
What is hair drug testing?
A hair drug test, also known as a hair strand test or a hair follicle test, involves analysing samples of head hair or body hair for the presence of drugs and their metabolites.
When a person consumes drugs, they are passed into the bloodstream, and the parent drug and a proportion of the drug’s metabolites enter the hair follicle. When the hair is subjected to analysis, the parent drug and its metabolites can be identified within the hair.
Hair drug testing is routinely used within family law and forensic fields and is renowned as being the gold standard in toxicological analysis. At AlphaBiolabs, our hair drug testing is 100% accurate and reliable, based on the hair samples received at our laboratory.
How does head hair drug testing work?
Head hair drug testing requires a cut hair sample to be analysed for the presence of drugs and their metabolites. When drugs are consumed and enter the system, part of the drug enters the hair follicle and is trapped in the innermost layer of the hair shaft, the medulla.
It takes around 7-10 days for the hair follicle containing the drug to grow above surface level and a further two weeks for the hair to be included in a cut sample. The rate at which head hair grows enables us to determine a pattern of drug use over certain periods, but this depends on the length of hair in the sample.
There are two types of head hair drug testing: segmented analysis and overview analysis.
Segmented analysis, which is the most detailed type of hair strand testing, involves segmenting the hair sample into 1cm sections for a month-by-month profile. This method can provide a detection window of up to 12 months and is favoured by those who need to identify a trend in drug use.
Overview analysis offers a more general insight into an individual’s drug use. In this method, the maximum length of hair that can be analysed is 3cm, which provides an overview of 3 months. This can be repeated up to four times to give a detection window of up to 12 months. However, rather than one 12-month overview, the 4 x 3-month overviews are reported separately.
The difference between segmented analysis and overview analysis is that segmented analysis enables you to determine the exact month a drug was consumed. Overview analysis only determines whether or not drug markers are present in a particular sample.
How does body hair drug testing work?
If head hair is not available for drug testing, body hair can be collected – from the face, chest, leg, arm, back or underarm.
Body hair grows at a different rate compared to head hair, and its growth isn’t consistent, which means it cannot be segmented to offer a month-by-month profile. Instead, body hair can only be used to provide up to a 12-month overview.
When body hair samples are collected, they are done so by weight rather than hair length.
How are hair samples collected and tested for hair drug testing?
For hair drug tests to be admissible in court, hair samples must be collected by a trained sample collector under strict chain of custody conditions to prevent tampering.
A head hair sample will be cut from an area around the highest point on the scalp, as this area has the least variation in growth rates. Samples must contain around 200 strands of hair and two samples are collected.
The samples are then transported to the laboratory and testing can begin. At AlphaBiolabs, all hair samples are washed three times to remove any surface drugs. This is because if someone has been in an environment that is heavily laden with drugs or they have been around someone else who has been smoking drugs, traces of the drug could be on their hair. Drug traces can also be transferred onto hair by direct contact. The washing solution is kept and can be analysed if required.
What affects a hair drug test result?
A hair drug test can confirm whether or not an individual has consumed drugs during a certain period. However, it cannot tell us the exact date, time, or method of ingestion.
There are certain factors that have the potential to impact the result of a hair drug test. For this reason, reputable laboratories like AlphaBiolabs will ask for full disclosure of any recent hair and beauty treatments, as well as current medical conditions and medications, so that this can be considered.
Some of the most common factors known to affect hair drug test results include:
Hair treatments
Bleaching, dyeing, perming, and straightening can all impact a hair drug test result. This is because the chemicals used in these types of treatments can damage the hair shaft and alter the concentration of the drug.
Hair colour
Studies show that the more melanin in the hair, the more likely that weak base drugs will bind to the hair. So, drugs like opioids, cocaine and methamphetamine bind more easily to darker hair, which results in higher concentrations of the drug in tests.
Hair growth rate and length of hair available
Hair drug tests can either analyse head hair, body hair or facial hair. Depending on the length of the hair being analysed, drugs can be detected up to 12 months after when the drugs were consumed.
The Society of Hair Testing (SoHT) advises that scalp hair from the posterior vertex should be the preferred head hair sample, as it offers the highest percentage of follicles in the anagen phase and the most consistent growth rate.
Scalp hair grows at an average rate of 1cm every month, meaning a 3cm sample can provide up to a 3-month window for drug testing.
Body hair and facial hair have a much more variable growth rate and more variable resting cycles compared to scalp hair, meaning that they can only provide up to a 12-month overview of drug use.
Environmental factors
Passive exposure to a drug through hands or smoke could potentially present a false positive reading. At AlphaBiolabs therefore, our rigorous hair drug testing processes include the decontamination of hair samples through a three-step chemical wash. The washed liquid is also kept at our laboratory for further analysis if required.
Cheating
For hair drug tests to be admissible in court, hair samples must be collected under strict chain of custody conditions to reduce the likelihood of tampering. However, some individuals will still attempt to cheat a hair drug test, which is why professionally-trained sample collectors must always be used to collect a sample.
Common ‘cheating’ methods include wearing a wig, trying to use someone else’s pre-cut hair, and even shaving off all body and head hair. AlphaBiolabs is a UKAS-accredited laboratory and only employs professional sample collectors, so you can rest assured that any attempts to cheat a hair drug test will be completely ineffective.
What factors are considered when compiling a hair drug test report?
The results of a hair drug test should never be interpreted in isolation. Several factors can influence how drugs are incorporated into the hair, meaning expert analysis is essential to ensure a fair and accurate assessment.
Factors that AlphaBiolabs’ Reporting Scientists will always consider when reporting hair drug test results, include:
- Hair type and colour – melanin levels in hair can impact drug incorporation, meaning darker hair may sometimes retain higher concentrations of certain substances.
- Cosmetic treatments – chemical treatments such as excessive bleaching, dyeing, perming or straightening have the potential to affect drug retention in hair strands.
- External contamination – environmental exposure to drugs (e.g. through smoke or physical contact) does not necessarily indicate use. Our reports consider the presence of metabolites – byproducts produced by the body after drug use – to help distinguish between active consumption and contamination. We also ensure the hair being tested is thoroughly washed first to ensure any surface contaminants are removed/minimised.
- Biochemical properties of drugs – different drugs bind to hair at different rates, meaning some substances are more likely to be retained than others.
- Variable growth rates of hair – Hair typically grows at an average rate of approximately 1 cm per month, as referenced by the Society of Hair Testing (SoHT). However, this rate can vary between individuals due to factors such as age, genetics, medical conditions, and ethnicity, potentially affecting the approximate time period represented by each hair segment.
What’s included in an AlphaBiolabs hair drug test report?
We are committed to delivering scientifically robust and transparent drug test results.
Our reports provide context and expert interpretation, ensuring that results are not taken at face value but considered holistically.
Our hair drug test reports include:
- Sample donor information – including photo ID, and details of any disclosures made at the time of the sample collection (e.g. prescribed medications, drug/alcohol usage, environmental exposure to illicit drugs/close body contact with a drug user).
- Substances found and detected levels – which drugs have been detected, along with their concentration levels, measured in nanograms per milligram (ng/mg) or picograms per milligram (pg/mg) of hair (analyte dependent).
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Comparison with internationally-recognised cut-off levels – to ensure accuracy, the levels of substances detected are compared against scientifically validated thresholds. These cut-off levels play a fundamental role in helping to distinguish between actual drug use and potential external contamination.
AlphaBiolabs also has analytical cut-offs for each analyte that are higher than the SoHT cut-offs to take into account analytical variation. Therefore, when a positive result is reported, there is no doubt that the compound is present within that tested sample.
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Interpretation of the test results, including relevant caveats and considerations – a drug test report should not simply tell you whether the sample donor has tested positive or negative for a certain substance.
Our reports include expert analysis, considering factors such as possible external exposure to illicit substances, sample donor declarations, the presence of metabolites (which indicate active drug use), pattern assessments of active and previous drug use, and consideration of the natural variations in hair drug incorporation and rates of hair growth.
- Segmented analysis – if requested, hair samples can be segmented to provide an insight into a pattern of drug use over time, rather than a single result for the entire period (overview analysis).
- Contextual considerations – factors such as hair treatments, hair colour, sample donor declarations (such as prescribed medications/declared substance use), and the donor’s ethnicity are all carefully considered, to ensure a fair and accurate interpretation.
Where can I get a hair drug test?
AlphaBiolabs has extensive experience providing hair drug testing services for local authorities, family law professionals and social workers. We have invested in the very latest technology for our state-of-the-art toxicology laboratory, employing the very best scientists, so you can be confident of receiving a 100% accurate result.
We have a nationwide network of professional sample collectors, and all sample collections are performed under strict chain of custody conditions.
We also offer free sample collection for legally-instructed hair drug tests from our Dublin walk-in centre.
For expert advice on hair drug testing, or to request a quote, call AlphaBiolabs’ Legal team on 0140 29466 or email testing@alphabiolabs.com.
Alternatively, complete our online quote form, and a member of the team will be in touch to discuss your needs.
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Gail Evans
Technical Trainer at AlphaBiolabs
A professionally-trained forensic scientist, Gail joined AlphaBiolabs in 2012 and holds the role of Technical Trainer.
Her day-to-day responsibilities include delivering in-depth training sessions both internally and externally, covering DNA, drug, and alcohol testing.
Throughout her career at AlphaBiolabs, Gail has held a variety of roles, including within the Legal and Workplace sectors of the business.
Before joining the company, Gail was a practicing forensic scientist with 25 years’ experience working for the Forensic Science Service, attending scenes of crime, and analysing physical and biological material with potential evidential value.
Gail also holds qualifications in chemistry and is a Lead Auditor for the ISO 9001 standard, the international standard for quality management.
