A hair alcohol test is used to determine if a person has consumed alcohol over a period ~90 days and, in some cases, longer. The test determines the Etg in hair and is one of the most accurate and established methods for testing alcohol consumption over a period. EtG is a direct marker of alcohol consumption and is only produced when a person has consumed alcohol or has increased blood alcohol levels. EtG is absorbed into the hair via sweat and diffusion and contaminate the entire length of the hair.

Hair alcohol testing is unable to determine the exact day(s) on which alcohol had been consumed but can accurately establish whether there has been consumption over a period.

The value is an integrated result for the time covered by the hair section analyzed, typically over an approximate 3-month period. EtG testing has been presented as evidence in court proceedings and hearings and is established as reliable. EtG testing has been subjected to, and passed, scientific admissibility standards.

It is possible for binge drinking (consumption of very large amounts of alcohol in a short period of time) to result in a positive hair alcohol test. It is not possible to determine if a positive test represents chronic excessive alcohol consumption that was due to relatively consistent excessive drinking or to frequent binge drinking, or a combination of both.

The Society of Hair Testing is a group of experts that promotes research in hair testing technologies in forensic, clinical, and occupational sciences and facilitates scientific cooperation and exchanges among members. The Society of Hair Testing defines chronic excessive alcohol consumption as an average consumption of 60 grams of pure ethanol per day over several months. In the United States, one "standard" drink (or one alcoholic drink equivalent) contains roughly 14 grams of pure alcohol, which is found in:

• 12 ounces of regular beer, which is usually about 5% alcohol 5 ounces of wine, which is typically about 12% alcohol

• 1.5 ounces of distilled spirits, which is about 40% alcohol

The Society of Hair Testing 2019 consensus paper established, “A concentration greater than or equal to 30 pg/mg EtG in the proximal head hair segment with a length of 3 cm up to 6 cm strongly suggests chronic excessive alcohol consumption.”3 In other words, an average of 60 grams of alcohol daily is equivalent to ~ 4.3 beers/day over 90 day or ~385 12-ounce beers in 90 days. These are amounts required to have a hair concentration of at least 30 pg/mg EtG.

Any concentration of EtG above the reading of 5 pg/mg within a length of 3cm and up to 6cm strongly suggests the repeated consumption of alcohol.

Studies have shown that EtG testing results for axillary hair, i.e., underarm hair, are not as accurate as those for pubic hair. Subjects have had negative EtG scalp and axillary hair results but have been positive in pubic hair.

Using pubic hair is the most reliable alcohol hair testing method to determine whether a person is abstinent. The test has many causes of false negatives and almost no causes of false positives. The sensitivity tradeoff is made because, generally, false accusations from false positives could be more detrimental than false negatives. Notably, a negative test does not mean that the person did not consume alcohol during the period. Low or moderate alcohol consumption commonly results in a negative EtG hair test.

Per Kronstrand, et al., who studied subjects with low or moderate consumption

The overall objectives of the study were to develop a sensitive method for ethyl glucuronide (EtG) determination in hair and then investigate if a low or moderate intake of ethanol could be differentiated from total abstinence. Forty-four subjects were included in the study, 12 males (7 drinkers and 5 abstinent) and 32 females (14 drinkers and 18 abstinent). The study lasted 3 months and the female drinkers consumed one glass (16 g of ethanol) and the males consumed two glasses (32 g of ethanol) of wine (13.5-14%) daily. Hair samples were collected as close as possible above the skin and the proximal 2 cm were analyzed for EtG [via liquid chromatography with tandem mass spectrometry (LC/MS/MS)]. … Of those who drank two glasses of wine every day, four had measurable amounts of EtG in their hair (5-11 pg/mg), and [ ] only one of the females drinking one glass of wine EtG [had measurable amounts of EtG in the hair] (3 pg/mg). Among the 23 abstinent subjects two had traces of EtG in the hair. We conclude that persons who ingested 16 or 32 g of ethanol daily for 3 months presented with low concentrations of EtG in hair, well below the proposed threshold for overconsumption set at 30 pg/mg. In addition, none of those who ingested 16 g/day had concentrations over the proposed abstinence threshold of 7 pg/mg.

This study showed that male subjects could be drinking alcohol and have a negative test if consuming 1 to 2 glasses (32 g of ethanol) of wine (13.5-14%) daily. For example, the EtG test would not be positive in this case if the subject had less than one drink per day or minimal alcohol in the prior 90 days.

Although false positives are rarely reported, hair analysis can occasionally be manipulated to result in a false negative. Variables such as hair length, location of hair, presence of a follicle, cosmetic treatment, gender, and pathophysiological conditions influence the results and should be considered. For example, a recent haircut (resulting in shorter hair and a potentially narrower time being tested) can result in false negative when trying to assess the standard ~90-day period. As well, the use of bleaching or chlorine on hair prior to testing may result in a false negative. In one study, after 2 and 10 hours of incubation (soaking) in chlorinated water, EtG hair concentrations were reduced by 20 ± 12% (range: 4-33%) and 57 ± 6% (range: 52-65%) respectively. A decrease in EtG hair concentrations was also noted after soaking or incubating the hair in deionized or pure water.