Traditionally, people purchase sunscreen based on SPF ratings. However, SPF only protects against the UVB rays of the sun. While the UVB rays are dangerous, so are the sun's UVA rays. Thankfully, more and more sunscreen now offers UVA protection. Dr. Schultz explains how to find sunscreen with UVA protection and how to understand how much protection each provides. It is important to know the difference between UVA and UVB rays because one of them is much more dangerous than the other. UVA rays are the dangerous rays that cause cancer and premature aging of the skin, since they penetrate more deeply into the skin than the shorter wavelength UVB rays. UVA rays are present all year long, and can penetrate windows and even clouds. To protect yourself from these harmful rays, the next time you purchase a sunscreen make sure you buy one that says "PA+++." This rating system is inspired by the Japanese system of PA, or protection against UVA, and is adopted by American manufacturers because the American way does not have a consistent system for protection against UVA.