Warts are tan, brown, black, gray, or yellow benign (buh-NINE) skin tumors that appear primarily on the hands, toes, knees, and face. They're caused by a virus, and they rarely appear in children under age two. A child can get them by touching an infected person or from a warm, moist surface, such as the floor of a locker room. If they're not treated, the warts may spread to other parts of the body or to other people. Warts on the soles of the feet are known as 'plantar' (PLAN-ter) warts and can be very uncomfortable or painful. Warts usually go away on their own, but if they don't, there are both over-the-counter and prescription preparations to remove them. A dermatologist (der-muh-TALL-uh-jist) can remove them with a scalpel or an application of liquid nitrogen, which freezes the wart. The wart eventually falls off, and the skin heals. The earlier a wart is treated, the better the chance of a cure, although it's possible it may come back.