I've always been told that SPF30 protects you against 95% of UVA/UVB. I learned anything higher than that provides no additional protection. Until I came across this article that proves otherwise.
The following study was done by the American Academy of Dermatology and published December 29, 2017.
SPF 100+ sunscreen is more protective against sunburn than SPF 50+ in actual use: Results of a randomized, double-blind, split-face, natural sunlight exposure clinical trial
Joshua D. Williams, PhD, Prithwiraj Maitra, PhD, Evren Atillasoy, MD, Mei-Miau Wu, DrPH, Aaron S. Farberg, MD, Darrell S. Rigel, MD, MS
Background
The value of additional photoprotection provided by use of high–sun protection factor (SPF) sunscreens is controversial, and limited clinical evidence exists.
Objective
To compare the sunburn protection provided by SPF 100+ and SPF 50+ sunscreen in conditions of actual use.
Methods
A total of 199 healthy men and women (≥18 years) participated in a natural sunlight, single-exposure, split-face, randomized, double-blind study in Vail, Colorado. Each participant wore both sunscreens simultaneously during activities, with no use restrictions other than designation of the treatment area. Erythema was clinically assessed on the day following exposure. Comparative efficacy was evaluated through bilateral comparison of sunburn between treatment areas and erythema score, as evaluated separately for each treatment area.
Results
Following an average 6.1 ± 1.3 hours of sun exposure, investigator-blinded evaluation identified 55.3% of the participants (110 of 199) as more sunburned on the SPF 50+ protected side and 5% (10 of 199) on the SPF 100+ protected side. After exposure, 40.7% of the participants (81 of 199) exhibited increased erythema scores (by ≥1) on the SPF 50+ protected side as compared with 13.6% (27 of 199) on the SPF 100+ protected side.
Limitations
Single-day exposure may not extrapolate to benefits of longer-term protection.
Conclusion
SPF 100+ sunscreen was significantly more effective in protecting against sunburn than SPF 50+ sunscreen in actual use conditions.
This is a copy of the original article. You can find the original article via the following link.
https://www.jaad.org/article/S0190-9622(17)32908-0/pdf