What is EtPa testing for alcohol?

EtPa is an organic compound called ethyl palmitate. It is a fatty acid ethyl ester (FAEE) that is analysed alongside ethyl glucuronide (EtG) in head hair alcohol testing. The level of alcohol consumed will determine the level of these markers in the hair.

EtPa and EtG markers are absorbed via different routes and their levels can assist in assessing excessive alcohol use by an individual. They are both analysed in head hair testing because they are affected by external factors in different ways. EtPa is produced in the blood and incorporated into hair via sebum (an oily substance secreted by glands in the skin). Its level is measured in ng/mg (billionth of a gram per mg of hair). FAEEs are lipophilic and therefore not water soluble, so although not affected by hair washing, the amount of EtPa detected could be affected by the use of hairsprays, gels and wax.

EtG, on the other hand, is produced by the liver and incorporated into the hair mainly through sweat, and is measured in pg/mg (trillionth of a gram per mg of hair). It is hydrophilic, meaning that it is water soluble. As such, some EtG may be lost through the use of hair dye and excessive hair washing.

EtPa can only be measured in head hair

EtPa cannot be measured in body hair. For this reason, head hair is preferred over body hair for alcohol testing. However, body hair can be useful to measure EtG if head hair is not available. Chest, arm, leg and beard hair can be analysed to provide up to a 12-month overview.

Ideally, the minimum length of head hair for EtG and EtPa tests is a 3 cm section taken from nearest the scalp, around 200 individual strands (about the width of a pencil). This is consistent with the consensus on hair alcohol testing for chronic excessive alcohol consumption published by the Society of Hair Testing (SoHT) in June 2009. The result will be considered either above or below the recommended SoHT cut-off levels.

The levels of EtPa and EtG marker found in the hair can help determine if a person has been drinking chronically and excessively, and will show an overview of 3 or 6 months.

For expert advice on EtPa testing in hair and all alcohol testing solutions for members of the public, the legal profession or workplace customers, please call our Customer Services team on 0333 600 1300 or email us at

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