How Long Can Hair Alcohol Tests Detect Drinking?

Many people want to know for how long hair alcohol tests can identify if alcohol has been consumed. They can detect it much longer than either a breathalyzer or a saliva test. But their precision is low. And their reliability and validity is very poor.

There are two types of hair alcohol tests. One identifies FAEEs and the other measures EtG. That needs explanation

Tests for FAEEs

Most of the alcohol consumed by a person is metabolized or broken down and leaves the body. But some of the results of that process (called metabolites) are deposited in the hair.

Part of the alcohol reacts with fatty acids to produce esters. These are known as fatty acid ethyl esters or FAEEs. Four of these esters (ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate) are used as evidence of alcohol consumption.

FAEEs enter into the hair within the cells that form the strand of hair itself. These cells develop in the root beneath the surface of the skin. Then the hair carrying the cells grows through the skin. It takes any FAEEs with it.

In addition, FAEEs occur in the sebaceous or oil glands of the skin. These, combined with the sebum produced in those glands, move along the hair shaft. This material coats the entire length of hair with a layer of fat.

hair alcohol testsMany people treat their  cosmetically with bleach, dyes, perm chemicals, or other  substances. Some research suggests that FAEEs are not significantly affected by such products. But that important question remains unsettled.

Tests for EtG

The EtG alcohol test identifies drinking by determining the presence of ethyl glucuronide. It’s commonly known as EtG. This is another metabolite resulting from alcohol metabolism. EtG is attracted to water and is taken into hair through sweat. For this reason, it can be washed out of the hair by shampooing.

Scalp hair grows at about one half-inch (1.27 cm) every 30 days. Good labs will only test hair growing within about 2.5’“4 cm of the scalp. This limits the detection history period to about 90 days. The exact time depending on how fast the subject’s hair grows. And that also depends on the season of the year and other factors.

Knowing that most labs only test hair close to the scalp, some people shave their heads to avoid being tested. But hair from other sites on the body can be analyzed. Because such hair grows slower, its use extends the window of opportunity to detect possible drinking.

Facts about Hair Alcohol Tests

Hair alcohol tests cannot distinguish between abstinence and light to moderate drinking. But they can be used to identify frequent heavy drinking. Several points should be kept in mind.

• Bleaching, dying, perming or frequently shampooing may reduce the accuracy of alcohol hair tests.
• It is possible that the tests may give false positive results. That is, falsely report drinking when none has occurred. This can happen from coming into contact with products containing alcohol.
• EtG and FAEE tests are designed so the results give 10% false positive and 10% false negative results.  That is, one of every five tests is expected to provide false results.
• The analysis of the hair strand should be for a period of possible drinking covering a period of at least three months.
• The alcohol test results should never be seen as firm evidence of drinking.1

Resources on Hair Alcohol Tests

Albermann, M., et al.  A SPME-GC/MS procedure for the determination of fatty acid ethyl esters in hair for confirmation of abstinence test results. J Chromat Sci., 2014, 52(9), 955-960.

Auwarter, V., et al.  Fatty acid ethyl esters in hair as markers of alcohol consumption. Clin Chem., 2001, 47(12), 2114-2123.

Kintz, P. (ed.) Drug Testing in Hair. Boca Raton, FL: CRC Press, 2006.

Leyton V, et al.  Hair drug testing in the new Brazilian regulation to obtain professional driver’s license. Addict., 2015. ePub. DOI: 10.1111/add.12945. PMID: 25967396.

Pragst F., et al.  Are there possibilities for the detection of chronically increased alcohol consumption by hair analysis?  Foren Sci Int., 2000, 107, 201-223.


Endnote:  Lamb, H. Hair Strand Testing for Alcohol: Hair Today, Gone Tomorrow? Family Law Week, 2010.