Had Full Hysterectomy Surgery - Two Weeks Later Developed A

Had full hysterectomy surgery - two weeks later developed a very itchy bumpy (measles like) rash, in area of the wounds/stomach. Surgeon was out of town and prescribed Cephalexin. Per two medical professionals, wounds are healing and are fine (not infected) except now have a bad rash. I'm allergic to an unknown penicillin/antibiotic, so I have not taken the Cephalexin yet - since it is to treat a "bacterial" infection, and wounds are not infected? Just read that Toxic Syndrome rash is bacterial, still not sure if I should take the Cephalexin and risk an possible allergic reaction? Hoping for an OK to hold off a few more days (its now been a week), and call the surgeon or should I call my family practitioner first thing Tuesday? Then again, I'm thinking I should take the Cephalexin and see what happens - since the rash is not going away on its own? Any Advise? Thank you.