Sunscreen with sun protection factor (SPF) 100+ was significantly more protective against sunburn compared with SPF 50+ and should be recommended for prolonged and recurrent sun exposure, according to study results published in the Journal of the American Academy of Dermatology.
The study was intended to compare the protective efficacy of SPF 50+ and 100+ sunscreens under actual use conditions at a beach for more than 1 day. The cohort included 55 healthy participants who applied both sunscreens to a randomly assigned side of the face and body for 5 consecutive days. Blinded clinical evaluation of erythema by a single grader and colorimetry and diffuse reflectance spectroscopy were performed the morning after each sun exposure.
The first observation of sunburn exclusively on the SPF 50+ side occurred after 1 day, while it took 3 days of sun exposure for sunburn to appear on the SPF 100+ side. After 5 days, 31 (56.4%) subjects had more sunburn on the SPF 50+ side compared with 4 (7.3%) on the SPF 100+ side. Overall, mean erythema intensity demonstrated statistically significantly less erythema on the SPF 100+ side compared with the SPF 50+ side.
Investigators noted that they only monitored the initial sunscreen application, and only recruited one participant with Fitzpatrick skin-phototype I.
“SPF 100+ was significantly more effective in protecting against [ultraviolet]-induced erythema and sunburn than SPF 50+ in actual use within a beach vacation setting,” investigators concluded.
Kohli I, Nicholson CL, Williams JD, et al. Greater efficacy of SPF 100+ sunscreen compared to SPF 50+ in sunburn prevention during five consecutive days of sunlight exposure: a randomized, double-blind clinical trial [published online September 19, 2019]. J Am Acad Dermatol. doi:10.1016/j.jaad.2019.09.018