Effects of a Moisturizer and Emollient on the Stratum Corneum Assessed by Confocal Raman Spectroscopy in Patients With and Without Atopic Dermatitis: An Assessor‐Blinded Prospective Cohort Study
Risa Fukuda, Rena Hashimoto, Kyongsun Pak, Hazuki Yasuda, Naoko Mochimaru, Yukio Matsumoto, Megumi Kiuchi, Shiho Uematsu, Kazue YoshidaABSTRACT
Background and Aims
Atopic dermatitis (AD) is characterized by impaired skin barrier function and reduced moisturizing factors. Moisturizers and emollients restore the barrier through distinct mechanisms, but their longitudinal molecular effects on the stratum corneum (SC) are poorly characterized, particularly in barrier‐deficient skin. We assessed the time‐dependent effects of a cream‐type moisturizer (CM) and petroleum jelly (PJ) on SC molecular composition in adults with and without AD using confocal Raman spectroscopy (CRS).
Methods
In this assessor‐blinded prospective cohort study (November 2019–February 2020), 12 adults without AD and 12 with AD applied 0.5 g each of CM and PJ to randomly assigned right or left forearms once daily for 28 (+ 7) days. SC water content, natural moisturizing factor (NMF), ceramide, cholesterol, and lactic acid were measured by CRS at 0, 14, and 28 days; transepidermal water loss (TEWL) and SC hydration were also assessed. Welch's t ‐tests with Bonferroni correction compared days 0–14 and 0–28 (two‐sided, 5% significance).
Results
Twenty‐three participants (non‐AD, n = 12, 42.8 ± 8.0 years; AD, n = 11, 41.5 ± 9.1 years) completed the study. Ceramide increased over time, mainly in the upper SC: CM raised ceramide significantly in both groups, whereas PJ significantly increased ceramide across all layers only in the non‐AD group. CM significantly increased lactic acid across all layers in non‐AD participants and in upper layers of AD participants, while PJ had no effect. SC hydration rose with both agents in non‐AD participants but only with CM in AD participants. TEWL showed no significant changes.
Conclusion
Moisturizers and emollients exerted distinct effects on SC components. Moisturizers were superior, increasing ceramide and lactic acid in the upper SC of patients with AD, and appear better suited for managing skin barrier dysfunction.