In middle age, damage done to your skin decades earlier starts to show up. This can include the first signs of skin cancer. The good news: when caught early, it s 99 percent treatable. So monthly self-checks for moles or anything suspect are smart. In front of a mirror, examine your entire body, from your scalp (use a handheld mirror) to the soles of your feet, advises Jennifer Linder, MD, an assistant clinical professor of dermatology at the University of California, San Francisco.