Depth penetration of light into skin as a function of wavelength from 200 nm to 1000 nm

Louise Finlayson*, Isla R.M. Barnard, Lewis McMillan, Sally H. Ibbotson, C. Tom A. Brown, Ewan Eadie, Kenneth Wood

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

88 Citations (Scopus)
22 Downloads (Pure)


An increase in the use of light-based technology and medical devices has created a demand for informative and accessible data showing the depth that light penetrates into skin and how this varies with wavelength. These data would be particularly beneficial in many areas of medical research and would support the use and development of disease-targeted light-based therapies for specific skin diseases, based on increased understanding of wavelength-dependency of cutaneous penetration effects. We have used Monte Carlo radiative transport (MCRT) to simulate light propagation through a multi-layered skin model for the wavelength range of 200 nm – 1000 nm. We further adapted the simulation to compare the effect of direct and diffuse light sources, varying incident angles and stratum corneum thickness. The lateral spread of light in skin was also investigated. As anticipated, we found that the penetration depth of light into skin varies with wavelength in accordance with the optical properties of skin. Penetration depth of ultraviolet radiation was also increased when the stratum corneum was thinner. These observations enhance understanding of the wavelength-dependency and characteristics of light penetration of skin, which has potential for clinical impact regarding optimizing light-based diagnostic and therapeutic approaches for skin disease.
Original languageEnglish
Pages (from-to)974-981
Number of pages8
JournalPhotochemistry and Photobiology
Issue number4
Early online date9 Nov 2021
Publication statusPublished - Jul 2022


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