Usefulness of barrier function index based on water content and transepidermal water loss for evaluating efficacy of skin protective creams

The functionality of skin protective creams containing a film forming agent for enhancing barrier function was evaluated from the viewpoint of skin roughness prevention. The subjects were 15 healthy adults (7 females) without skin disorders ranging in age from 21-24 years (mean 22.1 years). Three sites on the medial side of the left forearm were used for measurements; an untreated control where no cream was applied, a small area applied with skin protective cream containing barrier ingredients, and a small area applied with skin protective cream containing no barrier ingredients. After repeated tape stripping for 20 times, transepidermal water loss (TEWL) and water content in the stratum corneum (SC) after applying skin protective cream were determined over time in each subject. Barrier function index was calculated based on TEWL and water content in the SC, and used to evaluate the effects of the barrier ingredients. For the untreated control, the initial mean value obtained at 0 hours, and then 1, 2 and 3 hours after skin protective cream application were 0.79, 0.70, 0.65, and 0.62, respectively. Those values for areas applied with cream containing no barrier ingredients were 0.42, 0.44, 0.43, and 0.41, respectively, while they were 0.39, 0.42, 0.39, and 0.40, respectively, for the areas applied with cream containing barrier ingredients. That later group showed the lowest values at each measurement time. Notably, high efficacy was seen for the cream containing barrier ingredients from 0 to 2 hours after application. These findings indicate that barrier function index is useful for evaluating the efficacy of skin protective creams.