transepidermal water loss / barrier
Normal passive water loss through the skin due to diffusion is called transepidermal water loss (TEWL) and reflects how the skin works as a barrier. The efficacy of products having an impact on the skin barrier can be quantified using TEWL measurements. The Tewameter® TM300 (Courage + Khazaka GmbH) which we use calculates the water vapour gradient across a specific area of skin. Comparison with an untreated control area allows you to make claims regarding the efficacy of your product.