I can't say for sure if they work but I haven't experienced any negative effects from it. I am good about using sunscreen nowadays but I take these as added protection for my skin. When I was a kid I had sunburns on the regular (fair skin, 80's child living along the the So Cal coast), and in recent years I've had to get multiple pre-cancerous things burnt off by the Derm so I started taking the Heliocare supplement. Polypodium Leucotomos is the the main ingredient in it so I switched to this brand instead since it's more affordable.