Bruising can be caused by physiological factors, medications, hemophilia and other reasons. 1. Physiological factors: more common in the summer, because the skin is exposed, the temperature is high, the vascular epithelial cell permeability is high, a little touch is easy to cause subcutaneous hemorrhage, resulting in subcutaneous bruising, and some patients will also be accompanied by localized skin swelling and pain and so on. 2. Drug factors: patients taking warfarin, may cause patients to appear pharmacological coagulation disorders, resulting in patients easy to bleed, when the body is hit by the outside, easy to cause more than capillary hemorrhage, the formation of bruises, bruises. 3. Hemophilia: hemophilia patients lack coagulation factors in the body, easy to cause bleeding more than the situation, after the body collision, capillary bleeding will lead to skin bruising. The body is easy to bruise once collision, also seen in idiopathic thrombocytopenic purpura, aplastic anemia and other diseases, should go to the hospital in time for examination and treatment.