The causes of bruises on the legs, which are not painful or itchy, mainly include abnormal coagulation function, immune system dysfunction and poor blood return, as follows: 1. Abnormal coagulation function: lack of certain coagulation factors in the coagulation system or excessive destruction of platelet count due to hypersplenism or splenomegaly, which causes thrombocytopenia, etc., can lead to abnormal coagulation function, causing local blood vessel rupture This can cause local bruising due to blood overflow; 2. Immune system dysfunction: This can lead to increased permeability of local blood vessels and blood overflowing out of them, which can cause local bruising; 3. Poor blood return: This includes abnormal blood return due to varicose veins, which can cause local bruising. It is necessary to go to the vascular surgery department of the hospital to do blood routine, coagulation system and lower limb vascular ultrasound to clarify, and pay attention to less activity, proper rest and elevate lower limbs when sleeping to promote blood circulation.