Urticaria (hives) are a very common eruption. They are both allergic and nonallergic causes. Hives are classified as acute and chronic. Hives lasting longer than 6 weeks are arbitrarily classified as chronic urticaria. Acute urticaria is often caused by exposure to medication or foods. The cause however in many cases is never determined. Angioedema is a hive-like reaction that occurs deeper and the skin. Angioedema may be caused by medications such as ACE inhibitors (lisinopril). There are rare hereditary forms of angioedema. Angioedema may be severe with airway obstruction which can be fatal.