The cause of age spots is well known: Too much unprotected exposure to the sun. The UV light of the sun causes free radicals which damage the cells and accelerate the aging process. This process is also known as "oxidative stress." This process takes place not only in the skin, but in the entire body. Externally, it is barely possible to detect any exposure to free radicals -- except for age spots. They occur mainly on the back of the hand, on the arms or on the face, and are an unmistakable sign of a progressive aging process.