What Causes Reddish Rash On The Breast

I have a deep red rash under my left breast and on it . its a half moon shape it seeps and smells not on other side . I am taking vagifem had a partial hysterectomy conserned am 60 going on 61 and have had it on both breast a couple of times within the last yr also have conditon called leukoplasia thats the reason for vagifem or I wouldnt take it