Black patches on the legs often mean a complication of varicose veins, known as bruising dermatitis. Varicose veins are divided into stages 0-6 in the international staging, and the appearance of bruising dermatitis, which is when light brown petechiae and petechiae appear on the skin and gradually fuse into patches, is the fourth stage of varicose veins. In varicose veins, stages 3-6 are all indications for surgery, and once bruising dermatitis appears, it means that surgery should be performed, and the patient is advised to have a vascular surgery visit and ultrasound to clarify the extent of the lower limb valves. If surgery is not possible, elastic stockings and medication are needed to prevent the disease from progressing to localized ulcers, i.e. polyposis leg or old rotten leg.