Hello, this is a condition that sometimes happens in young woman. It can be related to the menstrual cycle. Since I don t know more information about you - not even your sex - I suggest you check for coagulation factors defects. A basic screening test would include blood clotting time, activated partial thromboplastin time and international normalization ratio. A complete blood count can be helpful. Conditions that cause unexplained bruises, usually have nothing to do with the complete blood count but this is a basic (and broad) test to check for hematologic disorders, particularly those involving the platelet count. I hope I ve helped. If you d like more detailed information, please present the results of the tests I asked for and perhaps a good quality picture of the involved area. Kind Regards!