A single center, randomized, double-blinded, multiple-exposure evaluation of SPF 50+and SPF 100+sunscreens for prevention of erythema under actual use conditions.

Solar radiation is a prime factor contributing to skin cancer development. Daily application of broad spectrum sunscreen with sun protection factor (SPF) of 30 or above is a recommended component of photoprotection. The value of additional photoprotection provided by high SPF sunscreens is controversial, as there is limited evidence demonstrating clinical benefit of sunscreens with labeled SPF values above 50+. The current investigation aims to evaluate the difference in sunburn protection offered by SPF 50+ and SPF 100+ sunscreens over the course of multiple natural sunlight exposures in a typical usage environment. A randomized, double-blinded, single-center, split body and split face, multiple exposure study was conducted to assess the efficacy of two marketed sunscreens (SPF50+ and 100+) in the beach setting of St. Petersburg, FL. Healthy subjects, 18-60 years old, with Fitzpatrick skin phototype (SPT) I-III were eligible. Over five consecutive days of fixed sun exposure intervals, subjects were permitted unrestricted access to test sunscreens and instructed to apply to the designated side as they normally would. Clinical assessments of daily and cumulative erythema were made by bilateral sunburn comparison and erythema severity grading. Objective assessments included colorimetry (Δa*) and diffuse reflectance spectroscopy (DRS) (Δ oxyhemoglobin). Subgroup analysis based on gender, body site, and SPT was performed. Eighteen male and 37 female subjects completed (1 SPT I, 22 SPT II, and 32 SPT III, average age 45.2 years, range 19-59). Cumulatively, the SPF 100+ offered greater protection against sunburn than the SPF 50+ sunscreen, as determined by a significant treatment effect in bilateral sunburn comparison ( P \u3c .001) and an overall difference in erythema severity (SPF50+ 0.353 ± 0.288 vs. SPF100+ 0.274 ± 0.215; P \u3c .001). This protection was supported by colorimetry and DRS assessments ( P \u3c .001 and P = .003, respectively). SPF 100+ sunscreen was significantly better at preventing erythema on the shoulders and arms as well as the lower legs and feet. The significance of the findings was confirmed for both genders and both SPT II and III subjects. Use of SPF 100+ sunscreen offers significantly greater protection against the development of erythema and sunburn than SPF 50+ sunscreen in SPT I-III subjects in a typical use setting. These findings may have important implications for photoprotection recommendations as a component of skin cancer prevention