Researchers from Newcastle University, U.K., have identified how the visible and infrared (IR) components of sunlight can synergistically increase skin damage in conjunction with ultraviolet (UV) light. Published in The FASEB Journal (Jan. 16, 2020, online ahead of print), the study compared the effects of physiologically relevant doses of complete solar‐simulated light, as well as its individual components, on donated human primary dermal fibroblasts and epidermal keratinocytes. Investigators assessed three biomarkers of cellular damage—reactive oxygen species (ROS) generation, mitochondrial DNA (mtDNA), and nuclear DNA (nDNA) damage. Lead author Professor Mark Birch-Machin, a professor of molecular dermatology at Newcastle University’s faculty of medical sciences, said in a press release: “We protect ourselves from ultraviolet rays in sunlight using sunscreens to prevent sunburn, premature ageing and increased risk of skin cancer. However, along with UV, sunlight also contains visible and infrared light.” “It is important to consider that visible and infrared light may also be contributing to the damage our skin receives from the sun, and that it could be beneficial to protect our skin against these as well when UV is present.” The investigators observed a greater induction of ROS, mtDNA, and nDNA damage from the combined solar-simulated light with the inclusion of the visible and IR components of solar‐simulated light in primary fibroblast cells compared to primary keratinocytes (p<0.001). When they looked at the specific components of solar light, alone and in combination, researchers found that the UV, visible, and IR components of solar light synergistically increased ROS generation in primary fibroblasts but not primary keratinocytes (p<0.001). “ . . . we found that our skin cells are sensitive not only to the single UV, visible and infrared wavelengths but also to their interaction within sunlight,” said Prof. Birch-Machin. “This means on their own each is fine but when combined the effect is enhanced, like in boxing—the first blow, the UV, does the major damage and then the smaller jabs, punches two and three, represented by visible and infrared, topple the boxer to the floor.” “Visible and infrared on their own have a small effect on skin damage but their potency is increased dramatically when UV is present.” Prof. Birch-Machin said that these findings should not be a concern to individuals already engaging in good sun protection behaviour, but may help manufacturers of sunscreens to further refine their products by looking for ways to protect the skin from complete solar light.