How do sunscreens work? Expand Sunscreens work by using active ingredients that absorb, scatter, or reflect the UV radiation before it reaches the skin. By filtering out harmful UV rays, broad-spectrum sunscreens help to reduce the risk of skin cancer and premature skin aging, as well as help prevent sunburn. Source: "Sunscreens: How to Read a Label, Expert Tips Etc." Sunscreens: How to Read a Label, Expert Tips Etc. | Cosmetics Info. Accessed April 29, 2019. https://cosmeticsinfo.org/products/sunscreens-how-read-label-expert-tips-etc.