The common causes of purple blood on thighs are pregnancy, cold and superficial varicose veins. The main ways to deal with it are applying ointment, massage and surgery to improve it. 1. Pregnancy: pregnant women because of rapid fetal growth, abdominal skin elasticity can not meet the growth rate of the fetus, resulting in the formation of superficial capillaries exposed to extrusion of purple blood, which can be applied to prevent stretch marks oil products to soothe blood vessels extrusion, coupled with the massage lifting techniques to help the abdominal skin stretching, but most of them can only play a role in alleviating the role of can not be completely eradicated. 2. Cold: When the human body is in a very cold environment, the superficial capillaries show purple blood filaments due to the obstacle of blood circulation, and the thinner the skin, the more obvious the patient is, and it can be relieved by itself when it is in a warm environment or given warming treatment. 3. Superficial varicose veins: The purple color of blood filaments appears due to the expansion of capillaries that can not rebound because of standing for a long time or exertion, and the serious cases need to be relieved by surgical ligation of the veins, and need to wear compression stockings to prevent it. If the above symptoms occur, it is recommended to go to the hospital in time, after clarifying the cause of the disease, under the guidance of the doctor to carry out regular treatment as soon as possible.