Development of an in vitro Functional Assay to Evaluate the Occlusive Properties of Moisturizers on Dry Skin.

INTRODUCTION: Dry skin is a hallmark of impaired skin barrier function. Moisturizers are a mainstay of treatment to help the skin retain moisture, and there is a high consumer demand for effective products. However, the development and optimization of new formulations are hampered due to lack of reliable efficacy measures using in vitro models. METHODS: In this study, a microscopy-based barrier functional assay was developed using an in vitro skin model of chemically induced barrier damage to evaluate the occlusive activity of moisturizers. RESULTS: The assay was validated by demonstrating the different effects on barrier function between humectant (glycerol) and occlusive (petrolatum). Significant changes in barrier function were observed upon tissue disruption, which was ameliorated by commercial moisturizing products. CONCLUSION: This newly developed experimental method may be helpful to develop new and improved occlusive moisturizers for the treatment of dry skin conditions.

Rationale and Preclinical Evaluation of a Multimodal Topical Body Skincare Product for Toning and Tightening.

A novel tightening and toning cream (TTC) was designed to improve body skin quality at multiple levels by engaging several key pathways that contribute to skin function, strength, and integrity. Evaluation of gene expression in both human in vitro 3D skin and ex vivo skin treated with TTC demonstrated changes reflecting improved extracellular matrix and dermal integrity, lymphatic drainage, mitigation of inflammation, cellular clearance and recycling, and adipocyte metabolism. This study provides the rationale and preclinical support for the use of TTC as a standalone agent to improve body skin quality or in combination with body contouring procedures. J Drugs Dermatol. 2021;20(10):1041-1044. doi:10.36849/JDD.6401.

Greater efficacy of SPF 100+ sunscreen compared with SPF 50+ in sunburn prevention during 5 consecutive days of sunlight exposure: A randomized, double-blind clinical trial.

BACKGROUND: Beach vacations are high-risk settings for overexposure to ultraviolet radiation. OBJECTIVE: To compare the sunburn protective efficacy of SPF 50+ and SPF 100+ sunscreens under actual use at the beach. METHODS: A prospective, randomized, double-blind, single-center, split-body/face study of 55 healthy individuals. Each participant applied both sunscreens to randomized sides of the face/body for up to 5 consecutive days. Blinded clinical evaluation of erythema by a single grader and objective instrumental assessments, colorimetry, and diffuse reflectance spectroscopy were performed the morning after each sun exposure. RESULTS: After 5 days, 31 (56%) participants had more sunburn on the SPF 50+ side compared to 4 (7%) on the SPF 100+ side. Overall, mean erythema intensity showed statistically significantly less erythema on the SPF 100+ side compared with the SPF 50+ side. The first observation of sunburn exclusively on the SPF 50+ side occurred after 1 day of sun exposure, whereas that for SPF 100+ occurred after 3 days of sun exposure. LIMITATIONS: Only initial sunscreen application was monitored, only 1 participant with skin phototype I was recruited, and participants were recruited from a local beach area. CONCLUSION: SPF 100+ was significantly more effective in protecting against ultraviolet radiation-induced erythema and sunburn than SPF 50+ in actual use in a beach vacation setting.

Novel confocal Raman microscopy method to investigate hydration mechanisms in human skin.

BACKGROUND: Skin hydration is essential for maintaining stratum corneum (SC) flexibility and facilitating maturation events. Moisturizers contain multiple ingredients to maintain and improve skin hydration although a complete understanding of hydration mechanisms is lacking. The ability to differentiate the source of the hydration (water from the environment or deeper skin regions) upon application of product will aid in designing more efficacious formulations. MATERIALS AND METHODS: Novel confocal Raman microscopy (CRM) experiments allow us to investigate mechanisms and levels of hydration in the SC. Using deuterium oxide (D2 O) as a probe permits the differentiation of endogenous water (H2 O) from exogenous D2 O. Following topical application of D2 O, we first compare in vivo skin depth profiles with those obtained using ex vivo skin. Additional ex vivo experiments are conducted to quantify the kinetics of D2 O diffusion in the epidermis by introducing D2 O under the dermis. RESULTS: Relative D2 O depth profiles from in vivo and ex vivo measurements compare well considering procedural and instrumental differences. Additional in vivo experiments where D2 O was applied following topical glycerin application increased the longevity of D2 O in the SC. Reproducible rates of D2 O diffusion as a function of depth have been established for experiments where D2 O is introduced under ex vivo skin. CONCLUSION: Unique information regarding hydration mechanisms are obtained from CRM experiments using D2 O as a probe. The source and relative rates of hydration can be delineated using ex vivo skin with D2 O underneath. One can envision comparing these depth-dependent rates in the presence and absence of topically applied hydrating agents to obtain mechanistic information.

Realistic Sunscreen Durability: A Randomized, Double-blinded, Controlled Clinical Study.

BACKGROUND: Studies show that sunscreen under real-life conditions is often not reapplied and/or applied insufficiently. This study investigated the durability of 2 current sunscreens with different SPF protection over an 8-hour period under simulated real-life conditions. METHODS: Participants (n=24) were randomized into two study groups utilizing either 2 mg/cm2 (FDA testing concentration) or 1 mg/cm2 (real-life application levels) of sunscreen. Two current SPF 15 and 70 sunscreens were applied to test spots on each participant's back. SPF values were obtained at baseline, 3.5, and 8 hours after initial application, during which subjects completed 30 minutes of moderate exercise followed by 80 minutes of water exposure. RESULTS: Participants in both dose study groups revealed only a 15-40% overall decrease in their SPF protection 8 hours after application. The study group that received half the FDA test concentration of sunscreen achieved approximately half or less the labeled SPF. At 8 hours, the test sites that received SPF 70 maintained an average SPF greater than 64 (2 mg/cm2 application) and 26 (1 mg/cm2 application). Similarly, the SPF 15 product test sites revealed an in vivo protection of 13 (2 mg/cm2) and 7 (1 mg/cm2). CONCLUSION: This study demonstrates that current sunscreens may be durable on skin even following significant exercise and water exposure, suggesting that reapplication intervals may be longer than currently recommended. In addition, the higher SPF sunscreen maintained a skin cancer-protective level of SPF following extended use.

J Drugs Dermatol. 2018;17(1):116-117.

SPF 100+ sunscreen is more protective against sunburn than SPF 50+ in actual use: Results of a randomized, double-blind, split-face, natural sunlight exposure clinical trial.

BACKGROUND: The value of additional photoprotection provided by use of high-sun protection factor (SPF) sunscreens is controversial, and limited clinical evidence exists. OBJECTIVE: To compare the sunburn protection provided by SPF 100+ and SPF 50+ sunscreen in conditions of actual use. METHODS: A total of 199 healthy men and women (≥18 years) participated in a natural sunlight, single-exposure, split-face, randomized, double-blind study in Vail, Colorado. Each participant wore both sunscreens simultaneously during activities, with no use restrictions other than designation of the treatment area. Erythema was clinically assessed on the day following exposure. Comparative efficacy was evaluated through bilateral comparison of sunburn between treatment areas and erythema score, as evaluated separately for each treatment area. RESULTS: Following an average 6.1 ± 1.3 hours of sun exposure, investigator-blinded evaluation identified 55.3% of the participants (110 of 199) as more sunburned on the SPF 50+ protected side and 5% (10 of 199) on the SPF 100+ protected side. After exposure, 40.7% of the participants (81 of 199) exhibited increased erythema scores (by ≥1) on the SPF 50+ protected side as compared with 13.6% (27 of 199) on the SPF 100+ protected side. LIMITATIONS: Single-day exposure may not extrapolate to benefits of longer-term protection. CONCLUSION: SPF 100+ sunscreen was significantly more effective in protecting against sunburn than SPF 50+ sunscreen in actual use conditions.