Introduction Skin hydration in the stratum corneum plays an important role in skin condition, and skin efficacy properties are influenced by its hydration level. However, few studies have identified the correlation between changes in skin hydration content and skin characteristics by skin depth level. Aims This study aims to determine how changes in skin hydration at specific depth levels affect skin condition by long‐term tracking changes in hydration of stratum corneum and viable epidermis after usage of moisturizer. Methods Ten volunteers were recruited and subjected to in vivo confocal Raman spectroscopy to perform water content profiling at skin depths of up to 52 μm. Mechanical properties of skin were measured using Cutometer and Antera 3D. Skin‐elasticity and roughness values observed before and after 15 days of moisturizing emulsion use were compared to demonstrate the correlation between observed changes in skin efficacy parameters and skin water content at specific depths. Results Significant increase in relative water content at specific depths was observed in this study. Among mechanical properties of skin, only R4, R6, and R8 parameters demonstrated significant changes. Additionally, rates of change in values of the R6 and R8 parameters revealed a high correlation with water content changes at viable epidermis depths below the stratum corneum. On the other hand, skin roughness parameter showed a correlation with water content changes at the outermost layer of stratum corneum. Conclusion Results of this study indicate that skin elasticity is influenced by its hydration level at viable epidermis depths and skin roughness at stratum corneum each. This suggests that monitoring depth profiles of water content using in vivo confocal Raman spectroscopy provides a breakthrough in tracking the skin efficacy effect of topically applied substances.

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BackgroundAge‐related changes in scalp parameters affect hair quality and scalp condition. However, detailed data on biophysical parameters of the scalp across age groups remain scarce. We aimed to investigate the differences in scalp parameters between individuals in their 20s and 50s and analyze their sex‐specific variations.Materials and methodsTwo hundred participants (160 women and 40 men) were equally divided into 20s and 50s age groups. Biophysical parameters of the scalp, including elasticity, pH, trans‐epidermal water loss (TEWL), sebum production, desquamation, firmness, redness, and yellowness, were measured in the vertex, occipital, and temporal regions. Hair density and thickness were measured in the temporal region. The accumulation of advanced glycation end products (AGEs) in the skin was noninvasively measured in a subset of 60 women.ResultsSkin firmness and redness increased with age in women, whereas yellowness increased with age in both sexes. Sebum production and pH levels were significantly lower in the 50s age group than in the 20s age group, particularly in women. TEWL was lower in men in their 50s than in those in their 20s, particularly in the occipital region. A significant reduction in hair density was observed in the 50s age group in both sexes. AGE accumulation in the skin increased with age and was correlated with scalp skin yellowness.ConclusionAge‐related changes in scalp parameters have important implications for hair health and scalp condition. These findings emphasize the importance of considering age and sex when developing hair care strategies.