Though not infallible, alcohol tests are a dependable way to determine whether someone has consumed alcohol in the past few months.

An alcohol hair test can detect whether a person has consumed alcohol in recent months. Blood and urine tests are used for the same purpose, but their timeframe is limited to a few days or hours. These tests are often given together to better understand a person’s alcohol use.

Alcohol hair tests are used for many reasons. Unlike blood and urine tests, they provide a much longer window into a person’s alcohol consumption behaviors.

For example, the test results can show whether a person has consumed alcohol infrequently or if the results are more in line with someone who has alcohol misuse or use disorder. They can also determine whether a person has abstained from alcohol for months.

However, alcohol hair tests have some limits and may not be good for every situation. Keep reading to learn more about how these tests work.

Alcohol hair tests are accurate, but there are examples of false positives and false negatives.

Alcohol does not leave hair quickly. Once it’s broken down and absorbed into the hair follicle and strand, evidence of alcohol use can be detected for several months.

An alcohol hair test looks for ethyl glucuronide (EtG) markers. EtG is a direct marker of alcohol consumption, and it’s present only when a person has consumed alcohol or has had increased blood alcohol levels.

However, research has found these tests aren’t foolproof. Cosmetic hair treatments like bleaching and perming can interfere with results, as can alcohol-based perfumes.

Alcohol hair tests are considered very accurate, but testers will ask about your cosmetic and hair care practices to determine whether there could be an issue with test results.

A hair alcohol test can detect alcohol use for a longer window of time than blood or urine tests. Also, a hair alcohol test can indicate the level of use during that time.

While blood, urine, and breath tests give a snapshot of a few hours or days, the alcohol hair test looks at several months of use. This can help show whether a person is drinking less or more than a time before. It can also determine whether a person has abstained from alcohol for a long time.

Additionally, this test is relatively easy to conduct. A small sample of hair is needed, and it can be done in a quick appointment. Most tests will take hair samples from the head. Occasionally, samples may be taken from chest hair, armpit hair, or groin hair.

The Society of Hair Testing, a global network that offers guidance on the testing of drugs in human hair, has created guidelines for where samples should be taken and how they should be handled.

How long alcohol appears in a hair strand test depends on a few factors.

In most cases, alcohol will appear in a hair strand test for 1 to 6 months. It will take several weeks after drinking alcohol for it to show up in a test. Alcohol can then be detected for several months.

In some cases, alcohol may be detected longer, even years later. But most people will cut or trim their hair before that time, so hair tests may show results for only up to 3 to 6 months.

It’s difficult to know exactly how much it takes to produce a positive result because each person metabolizes alcohol differently. But it doesn’t take much.

Low EtG readings in test results can show whether a person has been drinking recreationally or socially. This could be as few as one or two drinks a week.

The concentration of EtG could also indicate whether a person drinks habitually or may have alcohol use disorder. Even a high concentration from one drinking episode would likely be high enough to produce a positive result.

An alcohol hair test can determine whether a person has consumed alcohol over some time. The test can usually detect alcohol use 1 to 6 months later. The hair sample is typically taken from the head but can be taken elsewhere from the body.

Though the test is considered accurate, some factors can produce a false positive or a false negative result. These factors could include cosmetic hair treatments and products.