What Can Distort a Hair Analysis?

Human hair is not only a natural adornment but also a very effective store of information. What can distort a hair analysis? Hair contains breakdown products of various substances consumed, including drugs and alcohol.

Provided hair has not been tinted, dyed, bleached or otherwise chemically treated, many substances can still be detected months after consumption. Tampering with a hair sample is almost impossible: collection procedures strictly ensure that the sample is the person’s own genuine hair.

Tampering beforehand is also virtually ruled out. Although some substances wash out over time, no reliable statements can be made about particular products or methods, explains MPU expert Monika Sedlmeier of www.emotionale-balance.info.

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What should I consider before a hair analysis?

Hair analysis is possible only if the person has enough hair of the required minimum length. The hair must also not have been dyed, tinted, bleached or otherwise chemically treated.

What can distort a hair analysis? These procedures can alter the results, potentially even to the participant’s disadvantage.

Practical tip: Can CBD be detected in hair?

Which medications can affect hair analysis?

Depending on whether testing concerns alcohol or drugs, certain medications can influence the result. In drug testing, psychiatric medication or methadone affects the findings.

For alcohol, alcohol-containing medicines such as cough syrup may appear in the result. The same applies to alcohol-containing sauces and desserts, as well as certain cosmetics.

During a specified abstinence period, these products should therefore be avoided as far as possible. If avoiding certain medication is impossible, a specialist may be able to certify this so that its use can be taken into account when interpreting the result.

Further reading: Can a single instance of consumption be detected in hair?

What can distort a hair analysis?

Hair analysis is a fairly reliable procedure capable of detecting certain substances months after consumption, but only if the hair has not been dyed, tinted, bleached or otherwise chemically treated.

Certain medications also affect results: psychiatric medicines and methadone can be detected, as can alcohol-containing cough syrups.

Caution is also needed with some cosmetics. Products ranging from aftershave and shower gel to deodorant may contain alcohol or chemicals that influence the result. Over time, many substances wash out of the hair and are no longer detectable.

The alcohol marker EtG is one example. Frequent, particularly intensive washing can significantly reduce its concentration. However, this does not provide a reliable method of influencing the analysis in your favour.

Shampoos such as AtoxOut Hair Cleanser and other preparations are sometimes sold online as products that can specifically wash certain substances out of hair. In fact, no product reliably has this effect unless used exactly as instructed. Buying one is therefore not a cure-all, but only a possible route to drug-free hair.

False positives from external contamination: passive smoke and hand contact

External contamination: the danger of a false positive from environmental exposure One of the most common factors that distort hair analysis is external contamination, particularly in drug screening. The laboratory must distinguish substances entering the hair through sweat, sebum or direct contact from those incorporated through the bloodstream.

Drug or alcohol residues may reach hair through touching contaminated objects or passive exposure to cannabis smoke. Accredited laboratories use special washing procedures to remove external contamination. Nevertheless, to be safe, avoid all contact with drugs and high-strength alcohol-containing products in your environment.

The influence of melanin and hair colour: physiological factors

Physiological factors: how hair colour can distort results Hair colour directly influences substance incorporation and is therefore an important factor affecting hair analysis results. Dark, thick hair contains more melanin. Since many drug molecules, particularly cocaine and opiates, have an affinity for melanin, they may accumulate more strongly in dark hair, producing higher measurements.

Conversely, light, fine hair may underestimate actual consumption because less melanin is available for binding. Laboratories are aware of this effect and consider it when assessing cut-off values.

The forensic chain of custody as protection against distortion

The forensic chain of custody: the best protection against tampering The most important answer to “What can distort a hair analysis?” is: almost nothing in an official setting. External manipulation attempts, such as cutting or dyeing hair, are prevented by the chain of custody and laboratory procedures.

Only samples collected under direct observation by a certified doctor or expert, immediately sealed and documented through a chain of custody are valid for the MPU. Such forensic sample collection completely rules out substitution or subsequent tampering.

Sources: What Can Distort a Hair Analysis?

• Negative Hair Analysis Despite Consumption – Facts, Not Tricks — Topics: cosmetic treatments including bleaching, dyeing and heat; low or infrequent exposure; environmental and handling effects including pools, sunlight/UV and detox shampoos.
• Negative Hair Analysis Despite Consumption – How Is It Possible? — Topics: hair colour and thickness, dyed or bleached hair, chlorinated pools, high-alcohol hair products and thresholds.
• Hair Analysis Is Not a Reliable Indicator of Cannabis Consumption — Topics: external contamination through sweat, sebum or passive smoking and incorrect interpretation.

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FAQ

Can dyeing or bleaching distort a hair analysis?

Yes. Chemical treatments can alter hair structure and partly wash out or destroy incorporated substances. Accredited laboratories therefore do not accept chemically treated sections for forensic evidence.

Can laboratories use body hair if scalp hair is missing or unsuitable?

Yes. If suitable scalp hair of at least 1–3 cm is unavailable, body hair can also be used. However, results must be interpreted cautiously because body hair growth and substance incorporation vary.

Can frequent washing with special shampoos remove drug or alcohol residues?

No. Residues are incorporated deep in the hair shaft and cannot be removed by simple washing. Forensic laboratories clean the sample thoroughly before analysis to remove external contamination, but the actual markers remain.

Does shaving the head or cutting hair very short prevent analysis?

Shaving can prevent scalp hair analysis for the desired period but does not lead to rejection of testing. The laboratory will instead use body hair or a urine screening programme.

Can passive cannabis smoking produce a positive hair result?

Yes. In very rare cases, heavy, repeated external contamination through passive cannabis smoke can produce detection. Accredited laboratories nevertheless always perform intensive surface cleaning to rule out these external distortions.

Can alcohol-containing hair products distort EtG hair analysis?

Theoretically, external use of alcohol-containing hair products may cause slight surface contamination. However, the laboratory washes the sample thoroughly before analysis to avoid false results caused by external substances.

Can I challenge a positive hair result if I deny consumption?

You can challenge it by commissioning independent reanalysis of the remaining sample at another forensic laboratory. This is advisable if the positive finding may have resulted from a measurement error or contamination.

Can certain medications or hair-growth treatments distort results?

Yes. Some medications, such as certain painkillers or prescription drugs, can affect hair analysis and produce false-positive results for particular drugs. Tell the laboratory about all medications in advance to allow correct interpretation.

What happens if the laboratory finds the sample was altered or tampered with?

If clear tampering, such as bleaching, is identified, the sample is classified as unusable and the abstinence programme is failed. This is reported to the driving licence authority and generally leads to rejection of the evidence.

Does natural hair colour, or melanin, affect results?

Yes. The natural concentration of melanin can influence incorporation of drug and alcohol markers. Dark hair tends to bind more substances than light hair, which can affect measurements.