SUNSCREENS FOR OPTIMAL PROTECTION EFFICACY 201 FORMULATION DES IGNED FOR EFFICACY Sunscreens are generally made of oil-in-water emulsions, with the fi lter dissolved in oil droplets dispersed in a water phase. When applied, the droplets spread over the skin sur- face to form an organized network of UV fi lters: the more evenly the emulsion spreads, the higher is the performance of the fi lter. New Netloc k technologyTM is based on a semicrystalline polymer (INCI C12-22 alkyl acrylate/hydroxyethylacrylate copolymer, L’Oréal, Clichy, France) that gels and stabilizes the oil droplets without the use of surfactants. The resulting emulsion consists of gel microdroplets that lock in the UV absorbers. After application, these gel droplets create an optimal fi lm on the skin with constant thickness, even coverage, and a fi ne, homoge- neous distribution of UV fi lters. This fi lm anchors and adheres to the microreliefs of the skin, conveying high effi cacy and resistance to stresses such as water, sweating, and sand. The SPF-enhanci ng properties of this technology is illustrated by the comparison of three oil-in-water emulsions containing the same association of UV fi lters (at the same concen- tration), with an expected SPF of around 50. The SPF was measured in vivo following ISO 24444–2010. The formulation based on the Netlock technologyTM yielded an SPF twice as high as the other formulations based on classical emulsifi ers (Figure 1). The resistance to stress afforded by this technology was evaluated by applying sunscreens on volunteers who then conducted normal daily activities, such as offi ce work (3 h), lunch, and workout on a treadmill (20 min), followed by the application of a water mist. The UV absorption capacity of the sunscreens was evaluated by pictures taken under UV light: the absorption capacity of the classical sunscreen reduced signifi cantly but remained unchanged for the sunscreen based on the Netlock technologyTM (Figure 2). Figure 1. SPF values of three sunscreens containing the same UV fi lters ass ociation (expected SPF 50): The sun- screen based on Netlock technologyTM obtained a SPF value twice as high as the other two sunscreen products.

JOURNAL OF COSMETIC SCIENCE 202 NEED TO DEMONST RATE CLINICAL EFFICACY Products with t he same SPF but different UVAPF produce markedly different results: (25–28). EVALUATION OF E FFICACY OF SUNSCREENS AGAINST UVB/UVA DAMAGE Prevention of D NA damage. In addition to triggering infl ammation, DNA damage acti- vates the p53 tumor suppressor gene, producing a protein that protects cells from malignant transformation. p53 protein expression following UV exposure provides a sensitive biological endpoint to evaluate sunscreen effi cacy against damage that may cause skin cancer. The protection provided by two SPF25 sunscreens with different UVAPFs was compared in human volunteers in outdoor sun exposure conditions. One contained a potent UVA fi ltering system (Mexoryl® SX, Mexoryl® XL, Avobenzone) with UVAPF14, and the other had UVAPF6. After self-application of 0.8 mg/cm2 product in average before morning and afternoon sun exposure, volunteers were exposed to 6 d of sun with increasing UV dose from 6 minimal erythema dose (MED) to 10 MED. Both sunscreens provided similar levels of protection against erythema, but the one with UVAPF14 showed better protection against p53 accumulation than UVAPF6 sharing the same UVB protection (Figure 3) (28). Protection of the immune system. UVA and UVB indu ce local and systemic immune suppres- sion, potentially involving Langerhans cells (LC), pivotal cells in antigen presentation (29). Protection against UV-induced immune suppression was demonstrated in a study comparing 0.8 mg/cm2 of two sunscreens with SPF25 but UVAPF14 vs. 6 during exposure Figure 2. Illustration of UV absorption capacity of two sunscreens evaluated by pict u res taken under UV light: After offi ce work, lunch, running on a treadmill and a 3-s water mist application, the UV-absorption of the classical sunscreen was visibly reduced whereas it remains unchanged for the Netlock technologyTM sunscreen.