Common causes of itching of the skin on the main part of the body may include contact dermatitis, atopic dermatitis, scabies infection, psoriasis, and folliculitis. Arms. Itching of the arms, especially the area at the bend of the elbow, can be due to atopic dermatitis. Other causes include xerosis (dry skin) and brachioradialis pruritus (itching along the upper arms, neck and shoulder blades related to sun exposure and nerve damage of the upper spine). Legs.