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.

SUNSCREENS FOR OPTIMAL PROTECTION EFFICACY 203 to UV doses of 6 MED to 10 MED. Both sunscreens partially prevented reductions in LC density and alterations to morphology (Table I). However, signifi cantly less LC damage was observed with the sunscreen offering the highest UVA protection (29). Protection agains t photodermatoses. Photosensitivity , an abnormal reaction to sun- light, mainly UVA, covers phototoxicity, photoallergy, and photodermatoses. The most common p hotodermatosis, polymorphous light eruption (PMLE), presents as an eruption of papules, reticulated erythema, vesicles, and pruritus after 1–2 d sun exposure. In outdoor study comparing the efficacy of two sunscreens with SPF50+ but UVAPF28 and 17 (SPF-to-UVAPF (PPD) ratios of 2.1 and 3.5, respectively), the sunscreen with the highest UVA protection provided better PMLE prevention (Figure 4) (30). Figure 3. p53 accumulation in human skin unexposed or after repeated sun exposure pro t ected by sunscreen with different levels of UVA protection. Signifi cantly lower p53 accumulation was noticed for sunscreen A (SPF 25/UVA-PF 14 ratio = 1.8) versus sunscreen B (SPF 25/UVA-PF 6 ratio = 4.2). Control = unexposed area. Results are means ± standard error of the mean. Table I Alteration of LC Density and Morphology after Cumulative Solar Simulated Radiations Exposure of Human Skin Protected with Two Different Sunscreens Unexposed Exposed with SPF25 – UVAPF 14 Exposed with SPF25 – UVAPF6 Number of human leukocyte antigen-DR + cells 815 ± 91 671 ± 85a 540 ± 110a,b Average surface of cells (μm2) 144 ± 17 103 ± 14a 89 ± 14a,b Number of subjects (n = 10). Data are represented in mean ± SD. DR is one of the MHc-Class II present antigens from outside of the cell to T-lymphocytes. a p d 0.05 versus unexposed site. b p d 0.05 versus skin protected by the SPF25 UVAPF14 sunscreen.