Bruising on a woman’s legs for no reason belongs to the phenomenon of subcutaneous hemorrhage, the causes of which are physiological factors and pathological factors (trauma, blood system disorders, drug factors, vitamin C deficiency, etc.). 1. Physiological factors: if long-term physical inactivity, lack of physical exercise, a long time of high salt and high fat diet, poor blood circulation in the body, easy to lead to increased vascular fragility, prone to capillary rupture bleeding, bruising can be seen on the skin. 2. Pathological factors (1) trauma: if a woman suffers trauma, damage to the skin, resulting in capillary rupture bleeding, subcutaneous bruising and thus see bruises on the skin surface. (2) blood system diseases: common diseases including primary immune thrombocytopenia, skin purpura, hemophilia, etc., people with these diseases, easy to see bruises on the skin. (3) Drug factors:such as long-term use of fluoxetine hydrochloride, sertraline hydrochloride, aspirin and other drugs, affecting the ability of blood coagulation, producing subcutaneous bleeding phenomenon. (4) Vitamin C deficiency:Patients suffering from vitamin C deficiency have increased permeability of capillaries and are prone to subcutaneous hemorrhage, fatigue, anorexia, weight loss and other symptoms. It is recommended that patients according to their own symptoms, such as suspected disease, timely to the regular hospital dermatology consultation, follow the doctor’s instructions for a clear diagnosis, active treatment, to avoid delaying the condition.