Suggest Treatment For Spreading Rash On Various Parts Of Body

I am a 37-year olf female with no prior medical history. I have a rash in various random places on my body (back of hands, forearms, back of neck, hairline, shoulder blades, chest, belly button). This has been going on for about 3 months and slowly spreading. Not all spots itch constantly, but when they do itch, it is very intense. My doctor recommended cortisone cream, but it has not helped.