A functional mechanistic study of the effect of emollients on the structure and function of the skin barrier

Background: Preventing relapses of atopic dermatitis (AD) through the regular use of topical products to repair the skin barrier defect is an emerging concept. It is still unclear if some commonly used emollients exert a positive effect on the skin barrier.Objectives: To determine the skin barrier effects of emollients commonly prescribed in the U.K.Materials and methods: Two cohorts of volunteers with quiescent AD undertook observer‐blind forearm‐controlled studies. The first cohort (18 volunteers) treated the volar side of one forearm with two fingertip units of Doublebase™ gel twice daily for 4 weeks. The second cohort (19 volunteers) undertook the same regimen using Diprobase® cream. Transepidermal water loss (TEWL), stratum corneum integrity and hydration, skin surface pH and redness were determined at the test sites before and after treatment.Results: Neither Diprobase® cream nor Doublebase™ gel significantly affected the underlying skin barrier function. Both emollients were associated with significantly increased skin surface pH immediately after application (by 0·8 ± 0·19 and 1·0 ± 0·18 units, respectively), and no erythema. Diprobase® cream artificially and transiently (6 h) improved permeability barrier function by 2·9–3·1 g m−2 h−1 TEWL and increased skin hydration by 6·0–6·2 units. Doublebase™ gel, containing humectants, was associated with a greater (between 10·1 and 13·0 units during the first 6 h) and more sustained increase in hydration, lasting more than 12 h following repeated use.Conclusions: Diprobase® cream and Doublebase™ gel are not associated with skin barrier harm and appear to be appropriate for AD treatment. While displaying emollient properties, neither formulation displayed an ability to actively improve sustained skin barrier function