Angioedema is a lesion similar to urticaria, a non-concaveable edema of the skin and mucous membranes. Angioedema can occur anywhere on the body, but is more common in areas with loose subcutaneous tissue such as the lips, eyelids, tongue, and external genitalia, and can cause asphyxia if it occurs in the larynx. The swelling of angioedema can occur within minutes of exposure to the sensitizer and can also be accompanied by urticaria. Angioedema differs from urticaria in that the edema occurs in the subcutaneous or submucosal tissues and is deeper, so the boundaries are not clear. In the case of urticaria, the edema occurs in the dermis, so the boundaries of the mass are clear. The swollen area of angioedema usually subsides within a few hours, or it may last for 2 to 3 days, leaving no trace after it subsides. The diagnosis and treatment of angioedema are the same as those of urticaria. Those with clear etiology should be avoided, and those with unclear etiology can be treated with histamine (H1) receptor antagonists, such as Pulsatilla, Petrone (imipramine), and Keminan, etc. For those with laryngeal edema, glucocorticoids and/or epinephrine should be used as early as possible to prevent asphyxia and death. Wang Lian Yun, Department of Allergy, Shanghai Renji Hospital