The gold standard for the determination of water loss via the skin is the measurement of transepidermal water loss (TEWL) by determining the degree of water evaporation (g/hm2) in a hollow cylinder which is placed onto the skin.
Examinations of transepidermal water loss of the skin are necessary in order to prove barrier-supporting efficacy. They can be applied for tests of washing and cleaning detergents to document how mild surfactants are via a protection of the barrier.
In order to analyse the efficacy of skin protection the repetitive skin irritation test is used. Over a defined period of time a skin protection product and a skin-irritating substance are applied repeatedly. Reactions are evaluated by measurements of transepidermal water loss (TEWL) and by measurements of erythema using a Chromameter. In addition, a visual scoring is conducted by an expert.