Background: Assessment of skin lipid replenishment and surface appearance requires standardized methodologies capable of measuring both skin-reflecting and barrier-related skin properties. The least-reflection factor (LRF) reflects skin shine and surface lipid presence and is influenced by skin shine and sebum levels. Furthermore, lipid replenishment of the stratum corneum is associated with barrier-related parameters such as skin hydration, transepidermal water loss (TEWL), and surface scaliness. Integrating the reflecting and biophysical parameters may provide a comprehensive approach for evaluating skin surface refinement and barrier restoration; however, standardized methodologies combining these parameters remain limited. Objective: To standardize and validate a reliable and reproducible methodological framework for assessing the LRF and skin lipid replenishment using biophysical measurements, focusing on skin shine, sebum levels, hydration, TEWL, and skin surface microrelief parameters. Methods: This single-center, exploratory, validation study used an open-label, split-face design, including fifteen healthy adult participants with normal to dry and sensitive skin. Each participant served as their own control, with a lipid-replenishing topical product applied to one facial site and water applied to the opposite site. Assessments included skin shine and LRF, sebum levels, skin hydration, TEWL, and skin surface microrelief parameters such as smoothness, roughness, and scaliness. Measurements were performed at baseline and 15 minutes after application under controlled environmental conditions. Results: Post-application evaluations at the test site demonstrated increased skin hydration by 46.20 ± 5.87 (p value <0.0001), reduced TEWL by 8.26 ± 0.63 (p value <0.0001), and improved surface smoothness by 361.70 ± 63.99 (p value <0.0001), skin shine by 4.14 ± 0.12 (p value <0.001), reduced skin sebum level by 11.99 ± 3.68 (p value <0.01) while control sites remained within physiological ranges. Skin surface shine remained unchanged, and sebum levels showed no variation, indicating that changes in the LRF were directionally consistent. Conclusion: This study established a standardized methodology for evaluating LRF and lipid replenishment-related skin changes using integrated skin reflectance and biophysical measurements. The methodology demonstrated the ability to detect instant changes in skin barrier function and surface morphology. LRF showed potential as a reflecting parameter associated with skin shine and surface characteristics, supporting its use in dermatological and cosmetic research evaluating skin surface quality and barrier restoration.
Patel et al. (Tue,) studied this question.