What Can a Hair Analysis Reveal?

Human scalp hair is more than a natural adornment. It is also a very good store of information. Hair can provide information about metabolism over a period of months. What can a hair analysis reveal?

Alcohol or drug use can therefore be detected through hair analysis. Detectable substances include the alcohol markers EtG (ethyl glucuronide) and FAEE (fatty acid ethyl esters). The breakdown products of certain drugs can also be found.

• Amphetamine
• Amphetamine derivatives
• Cocaine
• THC-COOH, a cannabis metabolite
• Methadone
• Benzodiazepines
• Morphine

Different substances are incorporated into hair to different degrees. Basic substances such as morphine, cocaine and amphetamine are stored particularly well. Even a single instance of use can, for example, be detected in hair.

Do different substances become incorporated into hair to different degrees? Basic compounds such as cocaine, morphine and amphetamine bind particularly well to hair. A hair analysis for the MPU can therefore detect even a single instance of use of certain substances.

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Can a single instance of alcohol consumption be detected in hair?

To detect alcohol consumption using a hair sample, the breakdown products EtG and FAEE are measured in the sample. What can a hair analysis reveal? These alcohol markers can be found in the hair sample, even when only very small amounts of alcohol have been consumed. Chocolates, sauces and medicines containing alcohol should therefore also be avoided during the abstinence period.

The required duration of abstinence generally depends on the blood alcohol level at the time of the offence. At a blood alcohol level below 1.6 per mille, proof of abstinence is therefore not required. Between 1.6 and 2 per mille, the abstinence period is at least six months if only one offence has been recorded. Above this level, or after more than one offence, at least 12 months of abstinence must therefore be demonstrated.

Practical information: Hair analysis for proof of abstinence

How long can a single joint be detected?

After smoking a joint, the intoxicating effect lasts around one to four hours. However, this does not mean that THC, the substance responsible, has completely left the body. Even smoking a single joint can be detected in a hair sample. However, these hair samples are often imprecise.

People who use permitted CBD products, which are also derived from hemp, may receive a positive result. The same applies to people who spend time in a room where THC products are being consumed.

In general, the period during which THC can be detected depends on several factors. These include the duration and intensity of consumption, as well as the person’s overall physical condition. THC cannot be detected in urine more than 36 hours after use; in blood, detection is generally possible for no more than 72 hours. A single instance of use can only be detected in hair after two weeks, but remains permanently stored there.

Recommended reading: How does a hair analysis work?

How long must hair be for proof of abstinence?

To detect drug or alcohol use through hair analysis, the hair must be a certain minimum length. Human scalp hair grows by an average of around one centimetre per month. To provide proof of abstinence from alcohol, two locks of hair, each three centimetres long, are taken.

When investigating possible drug use, two locks, each six centimetres long, are taken. These lengths correspond to periods of three and six months respectively.
If the person does not have sufficiently long or thick hair, urine screening is used as an alternative in most cases.

Detecting heavy metals and nutrients (medical use)

What can a hair analysis reveal beyond drugs and alcohol? Hair analysis also serves as a valuable biomonitor for assessing general health. It can identify deficiencies in essential minerals and trace elements, such as zinc and selenium, that are important for hair growth and bodily functions.

At the same time, toxic heavy metals such as mercury or lead can accumulate in hair, allowing hair analysis to be used as a precise tool for identifying chronic exposure to pollutants.

Specific detection of metabolites (forensic precision)

Forensic hair analysis targets not only the original substance, but primarily its breakdown products (metabolites). For example, to determine whether someone has actually consumed alcohol or whether there is merely external contamination, the marker ethyl glucuronide (EtG) is detected in the hair.

In cases of heroin use, detecting 6-monoacetylmorphine (6-MAM) is crucial. Only the detection of these specific breakdown products can legally establish what a hair analysis can reveal: actual consumption rather than environmental exposure alone.

Factors that can distort the result

To avoid jeopardising acceptance of their proof of abstinence, everyone should know which factors can distort hair analysis results. Cosmetic treatments, particularly bleaching and dyeing, can reduce the substances being tested for in the hair and therefore produce a false negative result.

The laboratory must also distinguish between actual consumption and external contamination, such as THC from passive smoking. For drugs, this requires a separate assessment; for alcohol, only untreated hair is usually acceptable because the metabolite EtG is analysed.

Sources:

• Freiburg University Medical Centre: Hair Analysis – Forensic Toxicology
• TÜV Nord: Hair Analysis for Proof of Abstinence FAQ
• Cosmedica: Hair Analysis – Looking into the Body Through the Hair

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FAQ

What can a forensic hair analysis reveal?

In forensic practice, it primarily reveals chronic or regular drug and alcohol use over a longer period. Its main purpose is to provide proof of abstinence for the MPU.

Can a hair analysis detect a single instance of drug use?

As a rule, a single instance or very occasional drug use cannot be reliably detected through hair analysis. Only above a certain frequency and quantity of consumption does the concentration in the hair become sufficient for a positive result.

Which drugs can be detected in hair?

The most common drug classes can be detected, including cannabinoids (THC), opiates (morphine, codeine), cocaine and the amphetamine group (MDMA, methamphetamine). Synthetic drugs and certain psychiatric medicines can also be detected, though often only on specific request.

How far back can a hair analysis look?

As a rule of thumb, scalp hair analysis can look back about one month per centimetre of hair. For forensic purposes, a maximum of 6 cm (six months) is permitted for drugs and 3 cm (three months) for alcohol.

Is hair analysis a reliable way to establish alcohol abstinence?

Yes, establishing alcohol abstinence by testing for the alcohol metabolite ethyl glucuronide (EtG) in hair is considered very reliable. However, strict rules apply to maximum hair length and cosmetic treatments.

Can hair analysis also identify nutrient deficiencies?

Yes, outside forensic practice, hair analysis is used to identify deficiencies in trace elements, vitamins and minerals. It provides a snapshot of nutrition and the body’s nutrient supply.

What exactly is detected in hair during drug analysis?

The active drug substances themselves and their specific breakdown products (metabolites), which have entered the hair structure through the bloodstream, are detected. Detecting metabolites is crucial for ruling out external contamination.

Can hair dye distort the analysis result?

Yes, bleaching or intensive dyeing in particular can change the concentration of substances incorporated into the hair. For alcohol analysis, cosmetically treated hair is therefore often not accepted as proof of abstinence.

What can a hair analysis reveal about heavy metals?

It can reveal chronic exposure to and accumulation of toxic heavy metals such as mercury, lead or arsenic in the body. This analysis provides information about possible environmental exposure.

Can body hair be used to determine what someone has consumed?

Body hair, such as beard, underarm or chest hair, can in principle be tested for substances, but is accepted only in exceptional cases when scalp hair is unavailable. Its growth rate is more irregular, making it harder to determine the precise abstinence period.