The feet are purple, and if you exclude the loss of color of shoes and socks, which makes the feet temporarily stained, it may be caused by disease, and should be examined in the hospital and treated according to the examination results. Common causes include the following: 1. Subcutaneous bleeding: If the patient has a recent history of foot trauma, it may be subcutaneous bleeding, which is often referred to as bruising. In the foot by direct smash, serious sprain, internal may produce soft tissue contusion, fractures and other injuries, injury to local fascia tissue or muscle tissue, capillary bleeding is not absorbed in time, and gradually formed subcutaneous hematoma, over time in the skin surface presented as purple; 2, cold or frostbite in the lower limbs: long-term cold or even frostbite in the foot will cause poor blood circulation, resulting in purple skin of the foot. To pay attention to warmth, enhance the ability to resist cold, avoid frostbite parts of water, keep dry; 3, lower limb ischemic diseases: such as deep vein thrombosis or lower limb aortic stenosis, etc., will cause poor blood circulation in the lower limbs, resulting in purple, cold, numbness and other symptoms of the lower limbs. The corresponding treatment should be carried out for different diseases to increase the blood supply to the affected limbs, improve the ischemic state and relieve clinical symptoms; 4. Severe hypoxia: if there is asphyxia or serious heart and lung related diseases, the phenomenon of turning purple at the end of the limbs, i.e., the feet and hands, requires timely oxygen intake and transportation to the hospital for consultation and treatment.