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A study tested sunscreen use under typical conditions, comparing the effectiveness of sunscreens rated at SPF50 and SPF100.
It is usually assumed that the higher the sun protection factor (SPF) rating a sunscreen has, the greater the amount of protection it provides. Researchers from the Icahn School of Medicine and New York School of Medicine wanted to put sunscreens of different SPF protection levels to the test. This study was different from many previous studies, in that, these tests are typically conducted in a laboratory environment, rather than a real-world setting, where other factors come into play.
A total of 199 healthy men and women in Colorado, USA, participated in this randomized, double-blind study. The participants were given two bottles, one labeled for the right side of their face, the other, for the left side of their face. They were not told which bottle contained SPF50 and which contained SPF100 sunscreen.
SPF100 provided higher UV protection than SPF50 sunscreens
After a full day of sun exposure, participants were assessed by certified clinicians, 40.7 % of participants (81/199 individuals) had an increased score for erythema – an increased redness of the skin due to damage – on the side of their face that had SPF50, while 13.6% (27/199) of individuals had a higher score on the side with SPF100.
While this study helped bridge the gap in terms of lack of research on actual use of sunscreen with imperfect human use, there were some limitations. This study only assessed single day exposure and was unable to see if results would be impacted by long-term use of one of the two sunscreens tested.
New FDA guidelines on sunscreen
The FDA has recently called for further testing of specific sunscreen ingredients, as research has now shown that a significant amount is absorbed through the skin and into the bloodstream.
According to the FDA “Two ingredients (zinc oxide and titanium dioxide) are proposed to be safe and effective for sunscreen use and two (aminobenzoic acid (PABA) and trolamine salicylate) are proposed as not safe and effective for sunscreen use. FDA proposes that it needs more safety information for the remaining 12 sunscreen ingredients (cinoxate, dioxybenzone, ensulizole, homosalate, meradimate, octinoxate, octisalate, octocrylene, padimate O, sulisobenzone, oxybenzone, avobenzone).”
However, this should not be a deterrent to wearing sunscreen, “Given the recognized public health benefits of sunscreen use” it is recommended by the FDA that people “should continue to use broad-spectrum sunscreen with SPF 15 or higher with other sun protective measures as this important rulemaking effort moves forward.”
Written by Nikki Khoshnood, BHSc Candidate
Williams, J, D., Maitra, P., Atillasoy, E., Wu, M., Farberg, S, A., Rigel, S, D. SPF 1001 sunscreen is more protective against sunburn than SPF 501 in actual use: Results of a randomized, double-blind, split-face, natural sunlight exposure clinical trial. (December 29, 2017). Journal of the American Academy of Dermatology.
FDA sunscreen regulation changes fact sheet. Available at: https://www.fda.gov/media/124654/download