I Have Been Having A Rash On The Stomach, Back

I have been having a rash on the stomach, back , left side of torso and both arms. It started on the left side of torso as a whelp, but has since spread to the above areas. It itches and seems to be getting worse. Can prolong use of Tylenol PM cause this? I am allergic to Norco. It causes similar systoms.