Urticaria or hives is a relatively common form of allergic reaction that causes raised red skin welts that range upwards from 5 mm (about a 1/4 inch) in diameter, itch severely, and often have a pale border. Urticaria is caused by direct contact with an allergenic substance (generally a plant, such as poison ivy), or an immune response to food or some other allergen. Hives can also be caused by stress.

Angioedema (BE: angiooedema), also known by its eponym Quincke's edema and the older term angioneurotic edema, is the rapid swelling (edema) of the skin, mucosa and submucosal tissues. If it proceeds rapidly, it can lead to airway obstruction and suffocation, and it should therefore be treated as a medical emergency.

Hives as related to Angioedema