Suggest Treatment For Skin Rash

I have a red raised rash primarily under my arms and behind my knees, but is also in other spots on my arms and legs. It itches and is very sensitive to touch. I have been taking benedryl and using Aveno lotion and it is not helping at all. I had knee replacement revision surgery 7 weeks ago and my medication was recently lowered, I am taking Motrin 800 and oxycodone. I just stopped Cumidin 2 days ago. I have had shingles in the past and have minor exema. This rash is nothing like the exema that I have.