Hair follicle drug tests serve as a method for detecting past substance use by analyzing a small sample of hair. Many people wonder whether this type of test can also reveal alcohol consumption. The answer is yes, specific markers of alcohol use can be detected in hair.
The Basics of Hair Follicle Testing
A hair follicle test involves collecting a small sample of hair, cut as close to the scalp as possible. This sample, typically 1.5 inches (3.5 cm) in length, provides a historical record of substance use. As substances are consumed, they enter the bloodstream and are incorporated into the growing hair shaft.
The hair grows at an average rate of about 0.5 inches (1.3 cm) per month, allowing a 1.5-inch sample to provide a detection window of up to 90 days. Laboratories analyze these hair segments to identify traces of various substances. These tests are widely employed to detect illicit drugs due to their extended detection period compared to other testing methods.
Alcohol’s Presence in Hair
Hair tests do not look for alcohol itself (ethanol), but rather for specific byproducts the body produces as it processes alcohol. The primary markers detected are Ethyl Glucuronide (EtG) and Ethyl Sulfate (EtS). These are non-volatile metabolites formed in the liver after alcohol consumption.
Once formed, EtG and EtS enter the bloodstream and become incorporated into the hair shaft as it grows. These metabolites can also be deposited onto the hair through sweat and sebum produced by the scalp. These markers accumulate in the hair, remaining detectable for a much longer period than alcohol in blood or urine tests.
What Hair Tests Reveal About Alcohol Use
Hair follicle tests for alcohol are generally used to indicate chronic heavy alcohol consumption. They do not detect a single instance of drinking or moderate, occasional use.
Laboratories utilize specific cut-off levels for EtG and EtS to interpret the results. An EtG concentration below 5 picograms per milligram (pg/mg) is often considered consistent with self-reported abstinence. However, an EtG concentration greater than 5 pg/mg (or 7 pg/mg in some guidelines) suggests repeated alcohol consumption. A result of 30 pg/mg or higher indicates chronic excessive alcohol consumption, which equates to an average daily intake of around 60 grams of pure alcohol, or roughly 4.3 standard beers per day over the 90-day period.
Factors Affecting Test Outcomes
Several factors can influence the accuracy and interpretation of alcohol hair test results. External contamination is a concern; exposure to alcohol-based products like hair sprays, shampoos, or hand sanitizers can lead to detectable levels of EtG. While EtG is robust against external contamination, it is still a consideration.
Hair treatments, including bleaching or dyeing, may also impact test outcomes. These processes can alter the hair structure, reducing the concentration of metabolites within the hair shaft and leading to false negative results. Individual variations in hair growth rates can alter the detection window. Results from hair alcohol tests should always be interpreted by qualified professionals, often in conjunction with other forms of evidence or testing methods.