Sunscreen products with a sun protection factor (SPF) of 100+ are significantly more effective in protecting against sunburn than SPF 50+ sunscreen products, according to the results of a natural sunlight, single-exposure, split-face, randomized, double-blind study (ClinicalTrials.gov identifier: NCT02952235)1 published in the Journal of the American Academy of Dermatology.

The primary endpoint of the study was a bilateral comparison of sunburn on left- and right-side treatment areas. Scoring used a condensed 2-side difference scale: L1, participant’s left side noticeably more sunburned than his/her right side; 0, no difference in sunburn between the participant’s left and right side; R1, participant’s right side noticeably more sunburned than his/her left side. The secondary endpoint was erythema score using a 5-point scale: 0, no burn; 1, possible burn; 2, defined redness; 3, severe sunburn; and 4, edema and blisters.2


A total of 199 individuals were randomly assigned to treatment: 99 in group 1 (left SPF, 50+/right SPF, 100+) and 100 in group 2 (left SPF, 100+/right SPF, 50+). The study population comprised 115 men and 84 women; mean age of the participants was 37.4±16.3 years. The average exposure duration of the participants was 6.1±1.3 hours.

When blinded evaluation was performed the day after the sun exposure period, the SPF 50+ protected side of the face was reported to be significantly more sunburned than the SPF 100+ protected side of the face in 55.3% (110 of 199) of the participants, with 5.0% (10 of 199) of participants exhibiting results to the contrary (P <.001).

Sunburn severity, based on the mean increase in postexposure erythema score, was significantly lower on the SPF 100+-protected side of the face compared with the SPF 50+-protected side of the face (0.14±0.31 vs 0.330±0.44, respectively; P <.001). The highest postexposure erythema scores were reported on the SPF 50+ side of the face in both treatment groups. Overall, 40.7% (81 of 199) of participants had postexposure scores ≥1 on the SPF 50+-protected side vs 13.6% (27 of 199) of participants on the SPF 100+-protected side.

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The investigators concluded that SPF 100+ sunscreen products provide a level of enhanced sunburn protection that is observed after a single day of sun exposure. These findings suggest that sunscreen products with SPFs >50+ may offer improved sunburn protection in certain settings, having important implications for photoprotection recommendations as part of skin cancer prevention.

References

  1. Williams JD, Maitra P, Atillasoy E, Wu MM, Farberg AS, Rigel DS. 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 [published online December 29, 2017]. J Am Acad Dermatol. doi: 10.1016/j.jaad.2017.12.062
  2. Ou-Yang H, Jiang LI, Meyer K, Wang SQ, Farberg AS, Rigel DS. Sun protection by beach umbrella vs sunscreen with a high sun protection factor: a randomized clinical trial. JAMA Dermatol. 2017;153(3):304-308.