A wart is usually referred to as a common wart, which is a benign proliferation of the skin’s mucous membranes caused by an infection with the human papilloma virus. Wart blackening and hardening may be normal, or the wart may be necrotic. The first rash of common warts is a pin-cap-sized grayish-white flat papule with a rough surface. With the progress of the disease, warts gradually increase in size, obvious bulging, color deepening brown, the surface is dry and rough uneven, hard to touch. In addition, it is possible that the warts are growing too fast, the root of the warts appear a certain amount of ischemia, resulting in tissue necrosis, so that the warts become black, hard, after a certain period of time, warts may be off by themselves. If the warts become black and hard and accompanied by other inappropriate, you should promptly seek medical advice, follow the doctor’s instructions for further examination, in the doctor’s help to clarify the cause, for targeted treatment or treatment.