Abstract

Overexposure to the sun can have many harmful biological effects on the skin, from photoaging to skin cancers. Since ultraviolet (UV) rays have been identified as a cause of DNA damage and oxidative stress in the skin, the photoprotection provided by sunscreens is today assessed through their ability to filter UV light, using the sun protection factor (SPF). However, recent data have shown that high-energy visible light (HEV) can also cause biological skin damage. 
 
The aim of his work was to develop a new in vivo method for assessing the protection offered by photoprotectants over a wide range of wavelengths, including the HEV band, based on multispectral image analysis. 
This study thus assessed the absorption properties of six commercially available sunscreen products (five SPF 50+ products containing organic UV filters, one product containing the broad-spectrum filter TriAsorB™) and a control product containing no filters. 
 
Multispectral images were acquired from the skin of healthy volunteers' forearms, before and after application of the tested products. Images taken with LEDs emitting light at wavelengths ranging from UV to infrared were used to generate light reflectance maps for each product. Light absorbance levels in the UV and visible bands were then calculated. 
 
The product containing the TriAsorB filter showed significantly higher absorbance in the HEV band (380-450 nm) than the control product and other commercial sunscreens. All sunscreens tested showed the same absorbance level at 365 nm (UVA).

Multispectral imaging is therefore a simple and reliable in vivo method for assessing the actual protection provided by sunscreen products against all forms of photo-induced skin damage, including that induced by HEV radiation.