Background Aqueous Cream BP is widely prescribed to patients with eczema to relieve skin dryness. The formulation contains sodium lauryl sulphate (SLS), a chemical that is a known skin irritant and a commonly used excipient in personal care and household products. The chronic effects of Aqueous Cream BP application on skin barrier function have not been determined.
Objectives To characterize and assess skin barrier function of healthy skin after application of Aqueous Cream BP and to study the physical effects of the formulation on the stratum corneum (SC).
Methods The left and right volar forearms of six human volunteers were each separated into treated and control sides. The treated sides of each forearm were subjected to twice daily applications of Aqueous Cream BP for 4 weeks at the end of which concomitant tape stripping and transepidermal water loss (TEWL) measurements were made. The untreated sides of the forearms were not exposed to any products containing SLS during the study period.
Results Changes in SC thickness, baseline TEWL and rate of increase in TEWL during tape stripping were observed in skin treated with Aqueous Cream BP. The mean decrease in SC thickness was 1·1 μm (12%) (P = 0·0015) and the mean increase in baseline TEWL was 2·5 g m−2 h−1 (20%) (P < 0·0001). Reduced SC thickness and an increase in baseline TEWL, as well as a faster rate of increase in TEWL during tape stripping, were observed in 16 out of 27 treated skin sites.
Conclusions The application of Aqueous Cream BP, containing ∼1% SLS, reduced the SC thickness of healthy skin and increased its permeability to water loss. These observations call into question the continued use of this emollient on the already compromised barrier of eczematous skin.