New Methodology to Evaluate Sunscreens Under Outdoor Conditions: A Double-Blind, Randomized Intra-Individual Clinical Study of a Water-Based Broad-Spectrum SPF50+ Versus SPF15 (P3) and SPF50

Corinne Granger; Jean Krutmann; Javier Bustos; Yolanda Sola; Muzzammil Hosenally; Carles Trullàs; Philippe Andres; Thierry Passeron

doi:10.1007/s13555-019-00315-4

New Methodology to Evaluate Sunscreens Under Outdoor Conditions: A Double-Blind, Randomized Intra-Individual Clinical Study of a Water-Based Broad-Spectrum SPF50+ Versus SPF15 (P3) and SPF50

Dermatol Ther (Heidelb). 2019 Sep;9(3):589-599. doi: 10.1007/s13555-019-00315-4. Epub 2019 Jul 27.

Authors

Corinne Granger¹, Jean Krutmann², Javier Bustos³, Yolanda Sola⁴, Muzzammil Hosenally^{5

6}, Carles Trullàs³, Philippe Andres⁷, Thierry Passeron^{8

9}

Affiliations

¹ Innovation and Development, Isdin, Barcelona, Spain. corinne.granger@isdin.com.
² IUF-Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany.
³ Innovation and Development, Isdin, Barcelona, Spain.
⁴ Meteorology Group, Department of Applied Physics, University of Barcelona, Martí I Franquès 1, 08028, Barcelona, Spain.
⁵ Department of Economics and Statistics, University of Mauritius, Réduit, Mauritius.
⁶ Centre International de Développement Pharmaceutique, Phoenix, Mauritius.
⁷ Clipeum Pharma, Peymeinade, France.
⁸ Department of Dermatology, Centre Hospitalo-Universitaire de Nice, Université Côte d'Azur, Nice, France.
⁹ Inserm C3M (U1065), Nice, France.

Abstract

Introduction: This study explored a new method to test sunscreens in outdoor conditions (very high to extreme ultraviolet [UV] radiation) approximating real-life solar exposure while maintaining scientific standards and acceptable conditions, and assessed the efficacy of a water-based sun-protection factor (SPF) 50+ versus a reference SPF15 and two comparator SPF50+ products.

Methods: Thirty-five subjects underwent testing in summertime Mauritius. In each subject, five test areas were marked on the back. One area was left unprotected, and four sunscreens were applied to the others: investigational product (IP), SPF15 (ISO 24444:2010 reference standard P3), and two marketed SPF50+ controls. Subjects spent 1-2 h (depending on skin type) in the sun. After 24 h, erythema was assessed by clinical scoring (0-5) and colorimetry (a*, L*, and ITA). Secondary endpoints were correlation between clinical and colorimetry assessment, product tolerability, and total UV radiation received.

Results: All subjects were exposed to a very high UV index (≥ 8) and 30/35 were exposed to an extreme UV index (≥ 11). The IP showed statistically significant differences in clinical erythema scoring compared with unprotected skin and SPF15, but not with SPF50+ controls. On colorimetry, differences in a* (redness) and L* (lightness) reached statistical significance for the IP vs SPF15 but not vs SPF50+ controls. Clinical and instrumental erythema assessment correlated strongly (Spearman's rho 0.663). No tolerability issues were reported.

Conclusion: This exploratory study confirmed the ability of this outdoor model to discriminate sunscreens with different SPF using clinical evaluation as an objective measure. The water-based sunscreen maintained its efficacy in outdoor conditions of very high to extreme UV radiation: it was superior to SPF15 and comparable to SPF50+ controls in preventing erythema. The method used represents an option for sunscreen efficacy comparison outside of the laboratory.

Funding: Isdin.

Keywords: Outdoor; SPF; Sun protection; Sunburn.