In vivo method to evaluate antioxidative activity using UVA-induced carbonylated protein on human skin.

BACKGROUND: Skin is continuously exposed to oxidative stress caused by reactive oxygen species (ROS) produced by the ultraviolet (UV) light, and it is important to evaluate the antioxidant activity. Carbonylated proteins (CPs) are candidate markers of oxidative modification as a result from the ROS. We aimed to develop the CP-based method to assess the efficacy of antioxidants in human skin. METHODS: Ten healthy females were enrolled in the study to determine the UVA dosage for CP production, and another 10 females were included to evaluate the antioxidative activity. The stratum corneum was collected from test skin using D-Squame tape, and CPs from the SC were stained by fluorescence labeling and observed using a fluorescence microscope. RESULTS: CP level significantly increased with UVA irradiation from 15J/cm2 to 50J/cm2 compared to the control (non-UVA) area. CP production significantly increased by 34.38% and 35.22% in UVA irradiation and squalene (vehicle) areas. 5% α-tocopherol and ß-carotene significantly increased the CP production by 20.77% and 19.34% after 2 hours of 30J of UVA irradiation compared to control area. Inhibition rate of CPs in 5% α-tocopherol and 5% ß-carotene showed 41.45% and 45.37% after 2 hours of UVA irradiation. CONCLUSION: This study developed the simple, visual, and direct in vivo method to evaluate the antioxidative activity for products in human skin by measuring the CP level as an oxidative modification caused by UVA-induced ROS generation.

Layering sunscreen with facial makeup enhances its sun protection factor under real-use conditions.

BACKGROUND: The proper application of sunscreen is important to ensure protection of the skin against ultraviolet (UV) damage. Sunscreens are used in various ways in real world situations, which alters their UV protection efficacy. In this study, we simulated typical consumer use of sunscreen, which is often sequentially covered with facial makeup, in a laboratory study. METHODS: We compared the sun protection factors (SPF) of sunscreen and makeup products after consecutive layering of the products. RESULTS: The SPF of each sunscreen and makeup product was dramatically lower than stated on the label upon application of a typical amount used by a consumer, which is lower than recommended. For high-SPF products, the drop in effective protection was proportionally greater than those for the low-SPF products upon application of lower doses. However, layering sunscreen and makeup products greatly increased the effective SPF compared with that achieved by single application of each product, even when the amount of each product used was below the recommended level. CONCLUSION: Layering sunscreen with makeup may compensate for insufficient sunscreen application in real-life conditions by providing an additional source of UV protection and improving the homogeneity of coverage. Our results suggest that recommending consecutive application of sunscreen and makeup products may be a practical and useful approach to improving UV protection that would not require additional steps in the facial care routines of many individuals.

A novel in vivo test method for evaluating the infrared radiation protection provided by sunscreen products.

BACKGROUND: Infrared radiation (IR) exposure generates reactive oxygen species and induces matrix metalloproteinase-1 expression in human skin. Moreover, while not as acute as ultraviolet radiation, repeated infrared irradiation can result in the photoaging of skin. Broad-spectrum sunscreens can protect skin from IR, but no human in vivo test methods for the evaluation of sunscreens' IR protection effect have been developed. We aimed to develop such a method. MATERIALS AND METHODS: We included 155 Korean subjects in our three-part clinical study. The IR reflectance of subjects' skin was measured using a benchtop model of an IR light source and a reflectance measuring probe. We measured the IR reflectance in relation to skin color and hydration level to set up our experimental conditions. We then calculated the infrared protection factors (IPFs) of cosmetic emulsions as the IR reflectance ratio between cosmetic sunscreen-applied skin and non-sunscreen-applied skin and assessed the relationship between IPFs and the amount of sunscreen ingredients. Finally, this method was validated using several commercial sunscreen cosmetics. RESULTS: Skin color and hydration level did not influence the IR reflectance of subjects' skin. The IPFs of cosmetic sunscreens showed a positive correlation with the amount of inorganic sunscreen ingredients. CONCLUSION: In this study, we developed a simple, fast, and ethically acceptable human in vivo test method for evaluating the IPFs of cosmetic sunscreens.