An often-unacknowledged limitation is that exposure to psychoactive substances is typically not detectable within the first 1–2 weeks post-exposure. Therefore, while hair can allow us to detect exposure to substances within a wide window of time, it typically does not allow us to detect very recent use.
Hair testing has several drawbacks, including a small detection window, false positive results, outside variables that can alter accuracy, a high cost, and challenges interpreting the results. Additionally, there is a risk of prejudice, a breach of privacy, tampering, and a lack of uniformity with hair testing.
In fact, it is estimated that over 15% of all hair drug test interpretations will yield inaccurate results - a worrying figure that could have huge implications for your client. It might sound counterintuitive, but positive doesn't always mean positive, and this is where complications emerge.
Specificity of hair testing at standard laboratory cut-offs exceeded 90% for all drugs, but sensitivity of hair testing relative to self-report was low, identifying only 52.3% (127/243) of self-disclosed marijuana users, 65.2% (30/46) of cocaine users, 24.2% (8/33) of amphetamine users, and 2.9% (2/68) of opioid users.
Hair analysis provides good evidence in the fields of forensic and clinical toxicology, doping control, and occupational medicine, but do not demonstrate clear evidence in the fields of general health screening.
Given adequate hair length, hair testing can detect exposure to psychoactive substances within wide time-frames – much wider than with urine, blood, and saliva. However, hair testing cannot detect very recent exposure, and infrequent cannabis use in particular can be difficult to detect.
How far back can a hair drug test detect drug use? Hair drug tests have the longest detection period, and can typically detect drug use for up to 90 days. Depending on the drugs used, a hair sample can sometimes help determine when drug use occurred and whether it's been discontinued.
Here, we show evidence that peroxide treatment can, even after 15 minutes, completely remove incorporated cocaine and degradation products from the hair, making it impossible to identify cocaine users by hair analysis.
In theory, hair drug tests can be attempted to be cheated or manipulated, but it's not easy to do so effectively. Hair drug testing is considered tamper-resistant, which means that it is difficult to manipulate the results of the test.
Given how often most people cut their hair, hair analysis generally will not tell you anything about exposures that occurred more than one year ago. Furthermore, for most chemicals, hair analysis cannot tell you where a chemical in your hair came from.
Hair follicle drugs of abuse testing offers up to a 90-day window for detection of drug use and a convenient collection process that can be performed almost anywhere.
Although hair samples undergo a two-step testing process, they are not 100 percent accurate. Factors that can affect the concentration of drug metabolites present in a hair sample can include: the structure of drug compounds. the quantity of drugs a person has consumed.
Factors that affect test results include: Environmental exposures: Inaccurate results can also occur due to environmental exposure to drugs. For example, during exposure to secondhand smoke from cocaine or tobacco some of the smoke or vapor can enter the hair and lead to a positive test result.
Hair drug testing on dyed or bleached hair may still be worthwhile. Any chemical treatment such as hair dye, bleach, chemical straightening and permanent waves can damage the hair. This damage may lead to some of the drugs that may be present, being leached out from the hair.
Hair drug testing can detect a variety of drugs including, but not limited to: marijuana, cocaine, opioids (including codeine, morphine, heroin, and synthetic opioids), methamphetamine, ecstasy (MDMA), and PCP.
An evidentiary false positive that is the result of exogenous exposure to drug(s) in the environment. The drug positive result is not due to the ingestion or use of drug by any route of administration. Drug(s) in sweat or sebum from a source other than the user contacting hair to cause a drug positive result.
The Jerry G Method involves using bleach and hair dye to remove any drug metabolites from the hair follicles. These harsh ingredients can forcefully open your hair follicles to clear any traces of marijuana and other drugs.
For others, their hair detox journey can take about 14 days. There are a few factors that might affect the length of your detox: It could depend on your specific hair type, environmental pollution, the level of buildup you have from dead skin cells and styling products, and how frequently you wash your hair.
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.
Hair drug test collection
If the donor does not have head hair or if their hair is less than a ½ inch long, a specimen can be taken from other locations on the body. In order of preference, our collectors will cut the chest, underarm, leg, or facial hair to obtain a sample.
Factors Affecting Hair Test Accuracy
These include outside variables like hair care products, certain practices, scalp issues, hair length, and the substance being tested for. The accuracy of the results is also affected by the laboratory performing the test and the technique utilised to examine the material.
Intentional hair manipulation to avoid positive drug testing mainly relies on forced washing-out effects (“dilution of the hair”), for example, through extensive washing or even the use of commercially available cleansing shampoos advertised to produce negative hair testing results.