Skin cancer, the most common cancer in the United States, begins in the outer layer of skin (the epidermis). The best way to prevent this disease is to protect yourself from the sun and other sources of UV radiation. Sunscreen, especially broad-spectrum sunscreen (to filter UVB and UVA rays) with a sun protection factor (SPF) of at least 15, may help prevent skin cancer. However, it is still important to avoid the sun and wear clothing to protect your skin. Although some types of skin cancer are curable, people who have had the disease previously have a greater chance of developing another skin cancer.