Danazol is used to treat endometriosis (a condition in which the type of tissue that lines the uterus [womb] grows in other areas of the body and causes infertility, pain before and during menstrual periods, pain during and after sexual activity, and heavy or irregular bleeding)..Danazol is also used to treat fibrocystic breast disease (swollen, tender breasts with noncancerous lumps) when other treatments are not successful. Danazol is also used to prevent attacks in people with hereditary angioedema (inherited condition that causes episodes of swelling in the hands, feet, face, airway, or intestines). Danazol is in a class of medications called androgenic hormones