Expert: Dr.Paul Skett - 2/18/2010

Question
Hi Dr Skett. I'd like some information regarding hair alcohol profiling, particularly regarding accuracy and window of detection. I have read conflicting information. It seems to be generally accepted that the test can go back roughly 90 days with short hair, although some claim longer and others claim the test cannot be performed on hair shorter than half an inch at all. I have also read that only scalp hair can be tested, is this true? Apparently alcohol metabolites do not appear until 2 weeks after consumption, so would the 90 day window begin then or at the time of drinking? Is the accuracy of the test affected by any hair treatments? These details and any other relevent information would be greatly appreciated. Thanks.

Answer
Hi, Paul,

Thanks for your question.

This test measures the levels (or presence) of ethyl glucuronide (EtG) in hair - ethyl glucuronide is a minor by-product of alcohol consumption.

As with all hair analysis, it has to be interpreted carefully - it is thought that EtG is deposited in the hair root as the hair grows and appears on the surface (just where the hair breaks through the scalp) about a week later as the hair grows.

EtG is formed at the time of drinking but because of the time it takes for hair to grow (1cm per month on average) the EtG-containing hair will not appear above the scalp for about a week.

There is still controversy over whether hair treatments (washing, dyeing, perming)  can remove any substances from hair and this is equally true of EtG - theoretically any substance in hair should stay there permanently but evidence exists that any damage to hair through various treatments can remove at least some of the substances trapped there.

I have dealt with a case where drug use was traced back 12 months - after that hair ends tend to be a bit frayed and unreliable.

Hope this information is useful to you.

Best wishes,

Paul