What would cause a itchy rash on my back, arms and stomach. i am not allergic to anything.

There : There are many causes of a rash including eczema, psoriasis, medication reaction, internal causes, and many others. The most likely cause this time of year is probably eczema. To start with, i would recommend using cerave hydrating cleanser in the shower and use cerave cream twice daily. Consider a visit to a dermatologist if the problem persists. They can help diagnose you and prescribe more specific treatment depending on the type of rash you have. I hope this helps!

Many causes: Need to know more about the duration of the rash plus the drugs you are taking to even take a guess. If the problem lasts less than a week, it is more likely from a viral infection