A rare disorder characterized by recurring episodes of swelling of parts of the skin or mucous membranes. Sometimes internal organs may be involved. Symptoms can last for up to five days with usually weeks between episodes. Type 3 is due to a defect in Coagulation factor XII rather than a deficient or dysfunctional C1 (complex blood protein) as in types 1 and 2. This type is exacerbated by increased estrogen levels which can be caused by pregnancy or oral contraception. The severity of the disorder is variable with some patients only suffering episodes during pregnancy or after starting oral contraception. In other cases, adolescence triggered episodes. See also Hereditary angioedema, type III