Angioedema is swelling that is similar to hives, but the swelling is under the skin instead of on the surface.
Hereditary angioedema (HAE) is caused by a low level or improper function of a protein called the C1 inhibitor. With HAE the blood vessels are affected. An HAE attack can result in rapid swelling of the hands, feet, limbs, face, intestinal tract, larynx (voicebox), or trachea (windpipe).
Attacks of swelling can become more severe in late childhood and adolescence.
There is usually a family history of the condition. But relatives may be unaware of previous cases, which may have been reported as an unexpected, sudden, and premature death of a parent, aunt, uncle, or grandparent.
Dental procedures, sickness (including colds and the flu), and surgery may trigger HAE attacks.