Realistic Sunscreen Durability: A Randomized, Double-blinded, Controlled Clinical Study

January 2018 | Volume 17 | Issue 1 | Original Article | 116 | Copyright © January 2018


Hao Ouyang PhD,a Karen Meyer BS,a Prithwiraj Maitra PhD,a Susan Daly PhD,a Ryan M. Svoboda MD,b Aaron S. Farberg MD,c Darrell S. Rigel MDd

aJohnson and Johnson Consumer Inc, Skillman, NJ bClinical Research Fellow, National Society for Cutaneous Medicine, New York, NY cDepartment of Dermatology, Icahn School of Medicine at Mount Sinai, New York, NY dDepartment of Dermatology, New York University Medical Center, New York, NY

Abstract
Background: Studies show that sunscreen under real-life conditions is often not reapplied and/or applied insufficiently. This study investigated the durability of 2 current sunscreens with different SPF protection over an 8-hour period under simulated real-life conditions. Methods: Participants (n=24) were randomized into two study groups utilizing either 2 mg/cm2 (FDA testing concentration) or 1 mg/cm2 (real-life application levels) of sunscreen. Two current SPF 15 and 70 sunscreens were applied to test spots on each participant’s back. SPF values were obtained at baseline, 3.5, and 8 hours after initial application, during which subjects completed 30 minutes of moderate exercise followed by 80 minutes of water exposure. Results: Participants in both dose study groups revealed only a 15–40% overall decrease in their SPF protection 8 hours after application. The study group that received half the FDA test concentration of sunscreen achieved approximately half or less the labeled SPF. At 8 hours, the test sites that received SPF 70 maintained an average SPF greater than 64 (2 mg/cm2 application) and 26 (1 mg/cm2 application). Similarly, the SPF 15 product test sites revealed an in vivo protection of 13 (2 mg/cm2) and 7 (1 mg/cm2). Conclusion: This study demonstrates that current sunscreens may be durable on skin even following significant exercise and water exposure, suggesting that reapplication intervals may be longer than currently recommended. In addition, the higher SPF sunscreen maintained a skin cancer–protective level of SPF following extended use.

J Drugs Dermatol. 2018;17(1):116-117.

INTRODUCTION

The American Academy of Dermatology and US Food and Drug Administration (FDA) recommend reapplying sunscreen at 2-hour intervals.1,2 Sun protection factor (SPF) of sunscreens is tested with a 2-mg/cm2 application density.2 However, studies show that sunscreen under real-life conditions is often not reapplied and/or applied insufficiently.3 Recently developed sunscreen products claim to offer improved water resistance and photostability. This study investigated the durability of 2 current sunscreens with different SPF protection over an 8-hour period under simulated real-life conditions.

METHODS

Participants (n = 24) were randomized into 2 study groups utilizing either 2 mg/cm2 (FDA testing concentration) or 1 mg/cm2 (typical real-life concentration) application of sunscreen. Two current SPF 70 and 15 sunscreens (Neutrogena Ultra Sheer Sunscreen SPF 70, Neutrogena Corporation, Los Angeles, CA; Olay Complete All Day Moisturizer with Sunscreen SPF 15, Proctor and Gamble, Cincinnati, OH) were applied to test spots on each participant’s back (Figure 1). All participants and evaluators were blinded for study group and product placement. In vivo SPF values were obtained at baseline, 3.5 hours, and 8 hours post initial application according to the FDA standardized assessment utilizing the minimal erythema dose.4 Prior to the 3.5-hour assessment, subjects completed 30 minutes of moderate exercise (stationary biking). Prior to the 8-hour assessment, subjects completed 80 minutes of water exposure according to the FDA monograph on water resistance. This study was approved by IntegReview Ethical Review Board (Austin, TX), an independent Institutional Review Board.

RESULTS

Both dose study groups had a 15% to 40% overall decrease in their SPF protection 8 hours after application. At 8 hours, the test sites that received SPF 70 maintained an average SPF of 64 (2 mg/cm2 application) and 26 (1 mg/cm2 application). Similarly, the SPF 15 product test sites had an in vivo protection of 13 (2 mg/cm2) and 7 (1 mg/cm2) after activity.

DISCUSSION

These findings indicate that sunscreen products of both low and high SPF can maintain their efficacy following extended activity and time. The SPF of the products were approximately halved when using the 1-mg/cm2 dosage, consistent with
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