Hereditary angioedema (HAE) is a rare disease caused by deficiency of C1 esterase inhibitor (C1-INH). It is an autosomal dominant disease caused by a variety of mutations in the C1-INH gene. C1-INH is an important regulator of several pathways. One pathway it affects is the kallikrein–kinin pathway, which results in the generation of bradykinin. Bradykinin is an important mediator of edema. Diagnosis is based on low levels of C1-INH. HAE with normal C1-INH is also recognized in the literature and the pathophysiology is due to another aspect of the pathway being affected leading to increased bradykinin level. Bradykinin results in intermittent swelling of the cutaneous and mucosal surfaces. The swelling usually evolves over several hours and lasts a few days. Location of the swelling can involve any part of the body including fatal laryngeal edema. Newer treatments exist to treat acute attacks and reduce the frequency of future attacks. Earlier diagnosis and treatment of hereditary angioedema can prevent HAE-associated mortality. Statement of novelty: New treatments are used to treat these attacks. These treatments are aimed at patients having a more normal life with hereditary angioedema.