Film thickness frequency distribution of different vehicles determines sunscreen efficacy

@article{Sohn2014FilmTF,
  title={Film thickness frequency distribution of different vehicles determines sunscreen efficacy},
  author={Myriam Sohn and Adeline H{\^e}che and Bernd Herzog and Georgios Imanidis},
  journal={Journal of Biomedical Optics},
  year={2014},
  volume={19}
}
Abstract. Sun protection factor (SPF) frequently differs between sunscreens containing the same composition of ultraviolet (UV) filters that primarily define sunscreen efficacy. We tested the hypothesis that the thickness frequency distribution of the sunscreen film is also responsible for and can explain the divergence in the measured SPF. For this, we developed a method to measure film thickness from the difference of topography before and after application of 2  mg/cm2 of sunscreen on pig… 
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Repartition of oil miscible and water soluble UV filters in an applied sunscreen film determined by confocal Raman microspectroscopy.
  • M. Sohn, Th. Buehler, G. Imanidis
  • Chemistry, Medicine
    Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology
  • 2016
TLDR
Repartition of the UV filters within the sunscreen film upon application is investigated for its role to affect sun protection efficacy and Confocal Raman microspectroscopy was shown to be a powerful technique for studying this mechanism of sun protection performance of sunscreens.
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The possibilities of using alternative polymers for synthetic substrates for in vitro sunscreen testing are demonstrated, and four polymers showed a UV transmittance at 310 nm of more than 50%, as well as a total surface free energy close to the reported value for human skin.
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A quantitative relationship between wax concentration and significant responses was established, permitting the prediction of desirable rheological properties for improved sunscreen efficacy.
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TLDR
The results of this work show that the validity of the Beer–Lambert law is still given at the high concentrations at which UV absorbers occur in sunscreen films on human skin.
Skin Surface Topography and Texture Analysis of Sun-Exposed Body Sites in View of Sunscreen Application
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Different site-age combinations show significant variation of skin surface roughness, and the application of sunscreen may in some instances need to be adjusted to take into account the increased roughness of highly sun-exposed anatomical sites.
In vivo SPF and UVA-PF determination using (hybrid) diffuse reflectance spectroscopy and a multi-lambda-LED light source.
TLDR
A novel compact and adjustable DRS test system is presented, suggesting that the multi-lambda-LED device is suitable for in-vivo SPF testing based on the HDRS principle as well as for in -vivo UVA-PF measurements.
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