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The Science Behind Hair Testing

Did you know that this week (5-14th March) is British Science Week?

British Science Week is a 10-day programme of thousands of events running throughout the UK, with the aim of celebrating science, engineering, technology and maths.

To celebrate, we’ve taken a closer look at the science behind hair testing and the procedures that our Laboratory Scientists carry out every day to provide you with responsive, reliable results.

What’s in a strand of hair?

A hair sample can tell us a lot about an individual. Hair can be analysed to assess and understand exposure to heavy metals, such as mercury, and food allergies and intolerances.  At Lextox we analyse hair samples for illegal drugs, substances of abuse and chronic excessive alcohol consumption. This type of analysis is used by solicitors and local authorities as evidence in family law and child protection cases. It is also used by employers to ensure professionals are ‘fit to practice’ or as part of pre-employment testing programs.

How are drugs and alcohol incorporated into hair?

When a drug or alcohol enters the body, it is absorbed into the blood stream and the blood transports the drug and alcohol around the body. Every hair follicle has its own blood supply and it is this blood supply that feeds the hair with the nutrients it needs to grow. As the hair grows, drugs and alcohol markers are incorporated into the root of the hair and then into the hair strand itself. The hair therefore acts a bit like a tape recorder, recording anything that an individual has ingested or consumed over a period of time.  Because the hair is a solid material, drugs and alcohol markers will remain in that specific section of hair almost permanently, which allows Lextox to correlate it back to an approximate time period.

It’s important to note that it takes approximately 2 weeks for the hair to grow sufficiently above the scalp for inclusion in a cut sample.

The science behind hair drug and alcohol testing

After a sample arrives in our UK based laboratory, and the chain of custody checks have been carried out, the first job undertaken by our scientists is sectioning the sample. The hair is aligned in foil and then cut according to the testing required. Hair grows approximately 1cm per month, so a 3cm section of hair can cover an approximate 3-month time period.

When testing hair for drugs the hair sample can be segmented into monthly 1cm sections, to attain a month by month profile of drug use, or a whole 3cm (3 month) section which identifies drug use within that 3 month time period. When testing hair for alcohol it can be sectioned into either a 3cm or 6cm section.

As recommended by the Society of Hair Testing (SoHT), at Lextox every hair section is then washed individually prior to analysis, to minimise/eliminate any external contaminants that could be present on the outside of the hair. The use of methanol to wash hair samples is considered to be the most effective for decontamination, and is the method applied by Lextox.

Before the samples are analysed, they go through a 2 phase extraction process. The hair section is ‘cleaned up’ during the first stage, prior to the targeted extraction of the drugs themselves. It is during the second stage that we use a variety of solutions to discard unwanted compounds within the extract and to selectively elute our desired drugs into their own vials ready to be run on the instruments.

Our analysis is highly specific and sensitive, and we can detect drugs, metabolites and hair alcohol markers down to as little as a millionth millionth of a gram.

What can we learn from the laboratory analysis?

Once the laboratory analysis is complete, this information is then passed to our Reporting Scientists who will interpret the analysis results and prepare an Expert Report for use in court. In the case of drugs, we will be able to comment on the level of drugs/compounds detected and for alcohol whether there is evidence of chronic excessive alcohol drinking, which corresponds to an average consumption of 60 grams of pure ethanol (alcohol) per day over several months.

For more information or to instruct Lextox to carry out hair drug or alcohol testing, contact us on 029 2048 4141, [email protected] or via our website

Published 08/03/21 – All information correct at time of publication