The majority of the bruises on the thighs are caused by subcutaneous bruises, which may be caused by trauma and stimulation, the local subcutaneous capillaries rupture, and the blood inside the capillaries accumulates under the skin, you can choose to use hot towels or massage the legs often, which can accelerate the blood circulation in the legs and make the bruises absorb quickly. It may also be caused by thrombocytopenic purpura or allergic purpura later, need to go to the local hospital to do blood routine, if the development of eosinophil elevation, and in the bruise area accompanied by itching, should be allergic purpura, need to choose to use topical fluticasone propionate cream for treatment, if necessary, can be combined with oral loratadine tablets. If thrombocytopenia is present, it may be thrombocytopenic purpura and needs to be treated in hematology department.