EtG hair testing may soon become commercially available in the United States. There are numerous studies that show that hair testing may be accurate and helpful, however, it's important to realize that hair EtG has a much different meaning than that in urine. Hair is a repository matrix. It is not known how much drinking is neccessary for hair EtG to become positive, however, the amount is likely significant. Therefore, hair EtG testing is not a test that is sensitive for detection of abstinence (despite what some labs may caim). Hair EtG will not likely detect small amounts of drinking. When positive it does appear to be well correlated with amount of drinking over time.