Hair alcohol and drug testing is a highly sensitive method used to evaluate long-term patterns of substance use rather than recent or one-time exposure. By analyzing a small sample of hair collected close to the scalp, this testing can typically detect drug use over an approximate 90-day period, depending on hair length and growth rate. Hair testing identifies parent drugs and key metabolites, making it more resistant to short-term abstinence or attempts to evade detection. Alcohol use can be assessed through specific biomarkers, such as ethyl glucuronide (EtG), which indicate repeated or excessive consumption rather than incidental exposure. This method is frequently used in legal, child welfare, probation, return-to-duty, and high-level compliance settings. Strict collection, handling, and laboratory confirmation processes ensure accurate, defensible, and court-admissible results.