Site Overlay

Trace Levels of Drugs in Hair

The concern regarding traces of drugs from contact with another individual is a common question we get here at Lextox. The worry of being in contact with a known drug user through intimate sexual contact or from kissing could give a positive hair test result.

The levels detected by Lextox when a hair sample is analysed for drugs are very small, often being only a few nanograms (ng) of drug (a nanogram is one thousand-millionth of a gram). It is therefore natural for an individual to be concerned if they have been around traces of drugs or have had intimate contact with a known drug user that it could give rise to a positive hair test result, despite the individual not actually using the drug. The following aims to give further information regarding traces of drugs and the use of a drug on a single occasion.

Will my hair test result be positive from intimate contact with my partner who uses drugs?

Whilst it is theoretically possible for trace amounts of a drug to be transferred from a user to a non-user via close contact, the amount would be extremely small. As detailed earlier, Lextox can detect very small levels of drugs; however, Lextox utilises, where possible, the cut-off levels suggested by the Society of Hair Testing (SoHT) to indicate chronic (repeated) use of a drug. Trace amounts from intimate contact with a known drug user would therefore not be detected above the cut-off levels.

As such, your hair test result should not be positive from intimate contact with an individual who uses drugs.

I am living in shared accommodation and there are often traces of drugs on surfaces around the house. I don’t use any drugs myself, but could the traces around the house give a positive result if my hair was tested?

Environmental contamination is another issue Lextox often get asked about. When traces of drugs are present, they can inadvertently get on the donors hands which, if they rub their hands through their hair, can subsequently be on the hair. However, Lextox wash all hair samples prior to analysis to remove any compounds that may be present on the outside of the hair. This reduces the chance of a positive result being due to environmental contamination. Furthermore, where possible, Lextox also test for metabolites (breakdown products produced in the body when a drug is used). In addition, the levels of any drug present from environmental contamination would be extremely small and would not be detected above the Lextox cut-off levels. As such, a positive result would not be expected from being around traces of drugs.

I’ve only used a drug on a single occasion, would that give a positive result?

The minimum length of hair analysed by Lextox is 1cm. The population average hair growth rate is 1cm per month, as such a 1cm section covers an approximate one month time period. The use of a drug on one occasion only would not be expected to give rise to positive results as insufficient drug would be expected to accumulate in the hair to be detected above the cut off level. This is because almost all of the hair analysed would cover a time when drug use had not occurred. In addition, as detailed above, Lextox utilize the cut off levels suggested by the SoHT to indicate chronic (repeated) use. As such, the use of a drug on a single occasion would not be expected to give rise to a positive result.

Here at Lextox, our aim is to provide the best possible service, with expert and experienced  Laboratory Analysts and Reporting Scientists. All our experts are familiar with biological extraction and assessment techniques under ISO 17025 UKAS testing standards.

If you’re ready to get an expert review on drug and alcohol testing, , or ask any questions, please get in touch by calling 029 2048 4141 or emailing [email protected], and a member of our team will be in touch shortly.

Published 17/05/23 – All information correct at time of publication