Hair follicle tests analyze a small hair sample to detect substances. Unlike other drug screening methods with short detection windows, hair analysis provides insight into an individual’s substance use over an extended period, offering a historical record of consumption.
Understanding Hair Alcohol Testing
Hair drug tests detect alcohol consumption by looking for specific biomarkers produced when alcohol is metabolized, rather than alcohol itself. The two primary markers analyzed are Ethyl Glucuronide (EtG) and Fatty Acid Ethyl Esters (FAEEs). EtG is a water-soluble metabolite produced in the liver, deposited onto hair strands primarily through sweat glands. FAEEs are fat-soluble compounds formed from ethanol, incorporated into hair mainly from sebum, the oily substance secreted by glands on the scalp.
When alcohol is absorbed into the bloodstream, a portion converts into these metabolites. As hair grows, these metabolites become incorporated into the hair shaft, creating a chemical record of alcohol use. Both EtG and FAEEs are direct markers, meaning they are only present if alcohol has been ingested. Testing for both markers provides a more comprehensive picture, as they are affected differently by external factors.
Detection Times and Influencing Factors
Hair alcohol tests typically offer a detection window of up to 90 days. This timeframe is based on the average hair growth rate of about half an inch (1.5 cm) per month, with standard tests analyzing a 1.5-inch section of hair collected closest to the scalp. This provides a historical overview of consumption patterns rather than pinpointing exact dates of drinking.
Several factors can influence the accuracy and detectability of alcohol in hair. External contamination from alcohol-based hair products, such as hairsprays or gels, can potentially affect FAEE levels, leading to elevated results. Laboratories often request disclosure of such product use to aid in result interpretation.
Hair treatments like bleaching, dyeing, or excessive washing can reduce EtG levels because EtG is water-soluble. These chemical treatments open the hair’s cuticle layer, potentially decreasing marker concentrations. Individual hair growth rates also play a role; faster growth might shorten the detection window, while slower growth could extend it. The frequency and volume of alcohol consumption are also significant, as heavy chronic use results in higher biomarker concentrations compared to infrequent drinking.
Interpreting Hair Alcohol Test Results
A hair alcohol test result provides an integrated overview of alcohol consumption over the detection period, typically indicating patterns of use rather than isolated incidents. These tests are primarily designed to identify chronic heavy alcohol consumption, not occasional or single-instance use. For example, the Society of Hair Testing suggests an EtG concentration of 30 picograms per milligram (pg/mg) or higher in the proximal 3 cm hair segment strongly indicates chronic excessive alcohol use, defined as an average consumption of 60 grams of pure ethanol daily over several months. Lower concentrations (7-30 pg/mg) might suggest repeated alcohol consumption, while levels below 7 pg/mg generally do not contradict self-reported abstinence.
Thresholds are also established for FAEEs, with a cut-off value of 0.5 nanograms per milligram (ng/mg) often used to indicate chronically excessive alcohol consumption. While FAEEs are generally more resistant to hair treatments than EtG, both markers are typically analyzed together to provide a more reliable assessment. These tests are utilized in various scenarios, including legal cases like child custody disputes, employment screening, and sobriety monitoring programs. A positive result suggests a pattern of consumption consistent with chronic heavy drinking.