National Physical Laboratory

Better measurement of skin health

Trans-Epidermal Water Loss (TEWL) tests whether skin is working properly. It is used to identify invisible skin damage and monitor how fast skin recovers from burns. Doctors use it to monitor premature babies at risk of infection or dehydration before their skin is properly developed.


Industry uses TEWL to check the skin condition of workers exposed to industrial solvents, whilst researchers measure TEWL to identify the impact of skincare products.

These practices rely on TEWL measurement devices - but there has been a lack of calibration methods to ensure accuracy.

A joint industry project funded by the National Measurement System and led by NPL has now developed a new calibration technology for TEWL measurement. The prototype uses calibration wells, which produce a known rate of evaporation when primed with a measured droplet of water. Using several of these wells, each with a different rate of evaporation, the team can take readings with TEWL devices. They can compare the readings from each device with the known rates of each well to identify inaccuracies. A calibration calculation can then be developed and applied.

"TEWL instruments of different types can disagree by up to 50%," says NPL thermal measurement scientist Stephanie Bell,"which presents a huge margin for error considering TEWL's role in critical healthcare decisions. We are helping ensure users can rely on their equipment."

For further information, contact Stephanie Bell

Find out more about NPL's research in Biotechnology and Healthcare

Last Updated: 7 Jan 2013
Created: 11 Nov 2010


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