Topical supplementation with physiological lipids rebalances the stratum corneum ceramide profile and strengthens skin barrier function in adults predisposed to atopic dermatitis

Background People with atopic dermatitis (AD) suffer from dry, itchy skin with reduced skin barrier function that leaves it prone to irritant and allergen penetration. Alterations in the composition and structure of the stratum corneum (SC) lipid lamellae underpin this increase in permeability. A wide range of emollients is used to ameliorate the skin of patients with AD, but the majority have unclear effects on the lipid lamellae and barrier function. Objectives To compare the effects of a multivesicular emulsion containing physiological lipids and glycerine (MVE + GL) with a commonly prescribed oil-in-water emulsion containing glycerine without physiological lipids (O/W + G). Methods A double-blind intraparticipant-controlled study was undertaken in adults with a history of eczema. Participants applied MVE + GL to one forearm and lower leg and O/W + G to contralateral sites twice daily for 28 days. Skin properties were assessed before and after treatment. A detailed lipidomic profile was generated from SC samples, alongside in vivo attenuated total reflectance Fourier transform infrared spectroscopic analysis of its molecular composition. Results Fifty-eight people were included in the study [mean (SD) age 46 (21) years]. At sites treated with MVE + GL skin barrier integrity improved significantly [mean (SD) transepidermal water loss after 20 skin tape strips (TEWL20) 38.02 (18.64) g m–2 h–1 pretreatment vs. 29.79 (13.47) g m–2 h–1 post-treatment; P < 0.001], whereas O/W + G had no effect [35.6 (18.39) g m–2 h–1 vs. 37.4 (16.69) g m–2 h–1]. Concordantly, skin sensitivity to sodium lauryl sulfate (SLS) was significantly reduced by MVE + GL treatment [mean (SD) post-SLS TEWL 35.58 (15.43) g m–2 h–1 pretreatment vs. 29.54 (11.64) g m–2 h–1 post-treatment (P < 0.001); erythema was also reduced]. Skin moisture increased more rapidly at sites treated with MVE + GL vs. O/W + G, leading to a more rapid reduction in visual skin dryness. Over 1600 lipid species were detected in the SC. Ceramide species NP (non-hydroxy-phytosphingosine) and AP (α-hydroxy-phytosphingosine) with 18-carbon sphingoid bases, both ingredients of the MVE + GL, increased significantly by 24% and 19%, respectively, following MVE + GL treatment. In contrast, changes of 9% for NP(18) and 6% for AP(18) were not statistically significant at sites treated with O/W + G. Increased abundance of NP(18) species relative to NdS (non-hydroxy-dihydrosphingosine) species was related to improvements in skin barrier integrity. Conclusions While the glycerine-containing emollient reduced skin dryness, it had no impact on barrier function. In contrast, MVE + GL improved the physical integrity of the barrier and reduced the sensitivity of the skin.