Suggest Treatment For Rashes On The Lower Legs

Hello. I hve a rash on the bottom of both my legs it started out on my right like a pimple and very itchy, it grew about the size of a nickle, it really itches at night, same thing on my left leg to stop the itching I put Mederma and cortizone cream which does help but I would like for the rash to go away as well. My question is what is this rash and what can I put on them to get rid of them for good?