C1 esterase inhibitor is used to treat hereditary angioedema (HAE). HAE is a rare disease that causes swelling of the face, hands, feet, throat, stomach, bowels, or sexual organs. People who have HAE have low levels of C1 esterase inhibitor in their body, and this medicine increases the amount of C1 esterase inhibitor. Other resources and support can be found on the HAE Canada Website at – http://www.haecanada.org/about-us/