Study Compares Effectiveness of SPF50 and SPF100 Sunscreens

Research Background

A recent study evaluated the effectiveness of sunscreens with SPF50 and SPF100 ratings under typical usage conditions. The common assumption is that a higher sun protection factor (SPF) correlates with increased protection. Researchers from the Icahn School of Medicine and New York School of Medicine aimed to test this theory by comparing the two SPF levels in a real-world setting, as opposed to the controlled environments typically used in previous studies.

Study Design and Participants

The study involved 199 healthy men and women from Colorado, USA. It was designed as a randomized, double-blind trial. Each participant received two bottles of sunscreen, one designated for the right side of their face and the other for the left, without informing them which bottle contained SPF50 or SPF100.

Findings on UV Protection

After a full day of sun exposure, participants were evaluated by certified clinicians. Results indicated that 40.7% of participants (81 out of 199) exhibited increased erythema, or skin redness, on the side treated with SPF50. In contrast, only 13.6% (27 out of 199) showed heightened redness on the side protected with SPF100. These findings suggest that SPF100 offers superior UV protection compared to SPF50 under actual usage conditions.

Limitations of the Study

While this study contributes valuable insights into the effectiveness of sunscreens in real-life scenarios, it has limitations. The research focused solely on a single day of sun exposure, leaving unanswered questions regarding the long-term effects of using either sunscreen type.

New FDA Guidelines on Sunscreen Ingredients

In light of recent studies, the FDA has called for additional testing of specific sunscreen ingredients due to concerns about their absorption through the skin into the bloodstream. The FDA identified two ingredients, zinc oxide and titanium dioxide, as safe and effective for sunscreen use. Conversely, aminobenzoic acid (PABA) and trolamine salicylate were deemed not safe and effective. Additional safety information is required for 12 other sunscreen ingredients, including cinoxate, dioxybenzone, and oxybenzone.

Recommendations for Sunscreen Use

Despite the need for further testing, the FDA emphasizes the importance of sunscreen use. They recommend individuals continue to apply broad-spectrum sunscreen with an SPF of 15 or higher, alongside other sun protection measures, while the regulatory process is underway.

Conclusion

This study highlights the effectiveness of SPF100 over SPF50 in practical use, contributing to ongoing discussions about sunscreen safety and efficacy.

References

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

Press release: https://www.skincancer.org/media-and-press/press-release-2019/sunscreen-ingredient-absorption

Written by Nikki Khoshnood, BHSc Candidate.