Where is the rash? Is it near the incision? When I had my lumpectomy and reduction both of my breasts felt like they had prickly heat. Every bra and top I put on felt like sandpaper next to my breast from super soft cotton to silk nothing felt good. That prickly sensation finally resolved but it lasted nearly 3 months. And even still it's been 4.5 months and my one nipple still itches like crazy.