There have been many recent studies showing that the chemicals in sunscreens break down on a molecular level when energized by the Suns radioactive UV Rays. This break down leads to the development of free radicals which steel electrons from your DNA in order to stabilize themselves. This is a cascade effect because for each electron taken a new free radical molecule is created in its wake. This break down of your DNA and further replication of broken cells is known as abnormal cellular growth. When the process goes wild and the body can't stop it it's called cancer. The only way to stop the cascade of free radical damage is through the use of antioxidants. I am a licensed Esthetician who goes against the grain and actually promotes safe sunscreen-free sun exposure for arms, legs and torso for vitamin D production which is equally important to cancer prevention. Always protect your face with a good zinc-based SPF that is also loaded with antioxidants to prevent cellular damage that leads to aging. Safe exposure is no more than 20 minutes, then slather on some good zinc/antioxidant based body SPF which begins protecting you immediately because it is a physical blocker of the suns UV Rays as opposed to an absorber (chemical) which take 20-40 minutes to activate before they provide any protection!