What could be the cause of sore and itchy upper back muscles ?

Need more info: Itchy can be from a rash, not drinking enough fluid, allergic reaction to something you are wearing, or just normal. Diet can also influence...Junk food processed foods, sodas, etc can create inflammatory conditions n the body. Sore can be from working out, using muscles in new ways.... If none of that fits and you are just sore then see your doc for more evaluation.