Hi. My Name Is Joy. I Had Surgery Recently For

Hi. My name is Joy. I had surgery recently for the removal of a pituitary tumor. It went well and I was discharged and came home on 12/24. I noticed that I had a rash under my breasts. I used cortisone cream and it seemed to improve. I also took some benedryl. Today I noticed some itching on my arms and neck and looked in the mirror to see if anything was there. I noticed that the rash had spread. I took some Benedryl and took a nap. I am not sure what this is and how I should treat it. Any ideas?