How Long Can Hair Alcohol Tests Detect Drinking?

Many people want to know  how long hair alcohol tests can identify alcohol consumption.


I.   Hair Alcohol Tests

II.  Facts

III. Reliability

IV.  Summary

V.   Resources

They can detect it much longer than either a breathalyzer or a saliva test. But their precision is low. In addition, their reliability and validity are very poor.

I. Hair Alcohol Tests

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 a person drinks is metabolizes or breakes down and leaves the body. But some of the results of that process (called metabolites) go into the hair.

hair alcohol testsPart of the alcohol reacts with fatty acids to produce esters. These are fatty acid ethyl esters or FAEEs. Four of these esters (ethyl myristate, ethyl palmitate, ethyl oleate and ethyl stearate) are 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.

Many people treat their hair with bleach, dyes, perm chemicals, or other  substances. Some researchers think that such products don’t significantly effect FAEEs. But that important question remains controversial.

Tests for EtG

The EtG alcohol test identifies drinking by determining the presence of ethyl glucuronide (EtG). This is another metabolite resulting from alcohol metabolism. EtG goes into hair through sweat. However, shampooing can wash it out.

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.

Most labs only test hair close to the scalp. Therefore, some people shave their heads to avoid hait tested. But labs can also use hair from other places on the body. Because such hair grows slower, its use extends the window of opportunity to detect possible drinking.

II. Facts about Hair Alcohol Tests

Hair alcohol tests cannot distinguish between abstinence and light to moderate drinking. But they can identify frequent heavy drinking. It’s important to keep in mind several points.

• 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.
• Unfortunately, EtG and FAEE tests give about 10% false positive and about 10% false negative results.  That is, about one of every five tests gives false results.
• The analysis of the hair should be for a period of at least three months.
• The alcohol test results are never firm evidence of drinking.1

III. Reliability of Hair Alcohol Tests

Clearly, the tests are not very reliable. Thus, even when they give the same results, we can’t be confident. False positives can have especially serious, permanent consequences. That’s because test results tend to be used in important decisions by authorities.

  • hair alcohol testsFamily Courts
  • Employers
  • Criminal Courts
  • Probation Services
  • Law Enforcement Agencies
  • Return to Work Programs
  • Adoption Agencies
  • Rehab Facilities
  • Arbitrators

IV. Summary

So how long can a hair alcohol test detect drinking? If the drinking was heavy enough, it could be for about three to six months. But hair alcohol tests aren’t very reliable. So a person who has a drink occasionally may well escape detection. The big problem is when an alcohol abstainer is falsely seen as a heavy drinker. And if that person is hoping to adopt or to obtain custody. Or is falsely penalized because of a false positive reading.

hair alcohol testsNeither test can show whether drinking occurred while an employee was on-duty or off-duty. The U.S. Equal Employment Opportunity Commission has restrictions. Employers may not prohibit employees from drinking off-duty.

Both tests should be used together to reduce unreliability. But the findings should always be supported by other evidence. It might be be from a polygraph (lie detector), a PEth blood test, or other source(s).

So hair alcohol tests detect heavy alcohol drinking for about three io six months. They’re neither accurate nor reliable.

V. 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 increasing alcohol consumption by hair analysis?  Foren Sci Int., 2000, 107, 201-223.


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