Angioedema is an allergic reaction in the deep layers of the skin. In angioedema, large welts (wheals) develop under the skin near the eyes, mouth, hands, feet, or in the throat and tongue.

Angioedema may appear as a reaction to a substance (allergen). Allergens include medications, foods, insect bites, animal dander, and pollen. Angioedema welts also may appear during changes in temperature or emotional stress, or after an infection or illness.

Most cases of angioedema will go away within a few days without treatment. However, swelling in the throat can interfere with breathing and may be life-threatening. Angioedema also may be a sign of a more serious allergic reaction (anaphylaxis) that requires emergency care. Since angioedema can worsen quickly, a person with this condition should be evaluated by a health professional.