Hereditary angioedema (HAE) is a rare, potentially life-threatening disease that is characterized by unpredictable swelling of the subcutaneous tissues and mucosa. Several subtypes of HAE are now recognized, with the majority of cases caused by a deficiency in C1-inhibitor (C1-INH), herein referred to as HAE-C1INH. During an HAE attack, deficiency in C1-INH results in unopposed plasma kallikrein activation and increased levels of bradykinin, which results in the swelling and pain associated with the disease. Ecallantide is a highly specific and potent plasma kallikrein inhibitor approved for the treatment of acute attacks of HAE-C1INH. In two randomized, placebo-controlled, Phase III clinical trials, 30 mg of subcutaneously administered ecallantide demonstrated significant, rapid and durable symptom relief compared with placebo. The main safety concern following ecallantide is hypersensitivity reactions, including anaphylaxis. For this reason, ecallantide should be administered by a healthcare professional with appropriate medical support to manage anaphylaxis and HAE-C1INH.