What Causes Pimple Like Rashes To Appear After Hysterectomy?

Last week I had to have one of my ovaries removed along with both fallopian tubes. The only thing I Have left is 1 ovary. I had a hysterectomy last year due to fibroids and endometriosis. I recently developed a pimple like rash on my chest and now my upper back. I don't get rashes. I hav'nt changed detergents,soaps, ect... same with medications and food. I hav'nt changed anything. Can hormones or the surgery itself cause this type of rash. I'm confused where it came from. I was thinking maybe the drugs they gave me during surgery but, that was 10 days ago and I noticed the rash yesterday. any ideas??