Hives. Weals on the arm of a 69 year old male patient. Hives, also known urticaria, is a skin condition in which a rash of itchy wheals or lumps develops on the skin. Urticaria is most often caused by a non-allergic reaction to foods or drugs, although it may also be caused by heat, cold, chemicals, stress and allergies, among many other things. This case is secondary to a viral upper respiratory tract infection.