Skin rash?

A few hours after I woke up I noticed a bad rash on my arm, it goes all the way from my elbow to the tips of my fingers, its like little pin needle marks every where it covers my arm.I have never had anything like this before, and I am not allergic to anything as far as i know.What could this be?|||holy **** i just went to the doctor for that today im fbn serious i got 3 diffrent medicinesi bet ur itches alot too he said to take allergy pills for it to stop itchin u have an allergic reaction to something pretty soon it will start going from ur chest to ur stomach did u do nething new in the last 48 hrs good luck just take allergy meds|||Go see a doctor.|||Prickly heat from sweating at night or possibly bed bugs (yes they do exist) or fleas.|||THE ONLY THING I CAN THINK OF IS POISON IVY. IF THATS THE CASE YOU SHOULD HAVE INFECTED THE REST OF YOUR BODY. IF IT HAS SPREADED WASH THE SHEETS AND THE CLOTHES YOU WORE PRIOR TO BED TIME. AND THEN GO TO YOUR DOCTORS.