What Causes Itchy Rashes On The Torso And Arms With Ribs Pain?

HI, I had a rash that started friday, one week ago. I am having to take benadryl Q3-4 hrs for the itching. My face and back seem to be the only areas that dont end up with a rash. Its flat, but raises if I scratch it and gets hot. I haven't tried anything new at all. I have also had a slight cough for about a month. My ribs ache and my jaw is now starting to hurt. I have been to the doctors and they all seem to say the same thing, that its an allergic reaction. When i wake up in the morning, I always end up with a rash on my arms. Then as i get out of bed, and start getting ready, more spots start to appear. Should I be concerned. Keep in mind that I am a nurse that works in a hospital. So I am around all sorts of things