Generally only upper body itching is seen in cervical
nephropathy and in hyperthyroidism due to increased sweating. Hence MRI of cervical spine and Blood test to rule out thyroid disorders should be tried.
Other than that it could be urticaria or hives. Urticaria is usually triggered by allergens, such as drugs, foods, insect bites, inhaled substances, in response to sunlight, cold, heat, stress, exercise, or a viral infection.