In vitro skin model for characterization of sunscreen substantivity upon perspiration

Fatemeh Keshavarzi, Nina Østergaard Knudsen, Jonathan R Brewer, Morten F Ebbesen, Niloufarsadat Mirmahdi Komjani, Saeed Zajforoushan Moghaddam, Shadi Jafarzadeh, Esben Thormann*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Objective: The resistance of sunscreens to the loss of ultraviolet (UV) protection upon perspiration is important for their practical efficacy. However, this topic is largely overlooked in evaluations of sunscreen substantivity due to the relatively few well-established protocols compared to those for water resistance and mechanical wear. Methods: In an attempt to achieve a better fundamental understanding of sunscreen behaviour in response to sweat exposure, we have developed a perspiring skin simulator, containing a substrate surface that mimics sweating human skin. Using this perspiring skin simulator, we evaluated sunscreen performance upon perspiration by in vitro sun protection factor (SPF) measurements, optical microscopy, ultraviolet (UV) reflectance imaging and coherent anti-Stokes Raman scattering (CARS) microscopy. Results and conclusion: Results indicated that perspiration reduced sunscreen efficiency through two mechanisms, namely sunscreen wash-off (impairing the film thickness) and sunscreen redistribution (impairing the film uniformity). Further, we investigated how the sweat rate affected these mechanisms and how sunscreen application dose influenced UV protection upon perspiration. As expected, higher sweat rates led to a large loss of UV protection, while a larger application dose led to larger amounts of sunscreen being washed-off and redistributed but also provided higher UV protection before and after sweating.

Original languageEnglish
JournalInternational Journal of Cosmetic Science
Volume43
Issue number3
Pages (from-to)359-371
ISSN0142-5463
DOIs
Publication statusPublished - Jun 2021

Keywords

  • SPF
  • gelatin
  • perspiring skin simulator
  • substantivity
  • sunscreen
  • sweat resistance

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