In vivo method for evaluating sunscreen protection against high-energy visible light

BackgroundOverexposure to sunlight can have many harmful biological effects on the skin, leading to skin cancer and photoaging. As ultraviolet (UV) radiation has been identified as a cause of DNA damage and oxidative stress in the skin, the photoprotection provided by sunscreens is evaluated through their ability to filter UV light, using the sun protection factor (SPF). However, recent data have shown that high-energy visible (HEV) light can also cause biological skin damage.ObjectivesTo develop a new in vivo method for evaluating the protection provided by sunscreens across a broad range of wavelengths, including the HEV band, based on multispectral image analysis.MethodsThis study evaluated the absorption properties of six commercially available sunscreens (five SPF 50+ products containing organic UV filters, and one product containing the wide spectrum filter, phenylene bis-diphenyltriazine [TriAsorB & TRADE;]) and of a control product containing no filter. Multispectral images were acquired from the skin on the forearms of healthy volunteers, before and after application of the test products. Images taken with LEDs emitting light at wavelengths ranging from UV to infrared were used to generate light reflectance maps for each product. The levels of absorbance of light in the UV and visible bands were then calculated.ResultsThe product containing the wide spectrum filter exhibited significantly higher absorbance over the HEV band (380-450 nm) than the control product and the other commercial sunscreens. All the sunscreens tested showed the same level of absorbance at 365 nm (UVA).ConclusionsMultispectral imaging provides a simple and reliable in vivo method for assessing the real-world protection provided by sunscreens against all forms of photo-induced skin damage, including that induced by HEV radiation.