The development of large welts below the surface of the skin, especially around the eyes and lips. The welts may also affect the hands, feet, and throat. The condition is associated with allergies and histamine release.
Angioedema is a swelling similar to urticaria (hives), but the swelling is beneath the skin rather than on the surface. There seems to be a hereditary tendency toward the development of both angioedema and hives. Angioedema is associated with the release of histamine and other chemicals into the bloodstream, which is part of the allergic response.
Common allergens include:
Hives and angioedema may also occur after infections or illness (including autoimmune disorders, leukemia, etc).
Info found at yahoo.com