Suggest Remedy For Skin Rash On The Thigh

I Have had surgery on my foot last week. I have a itchy patchy rash almost like a prickly heat on my thigh above where 2 blocks were placed in my back of knee and inner thigh. After a few days the same rash appeared on my antecub where blood was drawn it is really itchy. I called the dr. They seem to think over the phone that the rash could be from surgeryy or my pain meds. No longer on the pain meds, still on lovenox but rash gets better then worse. any thoughts.