Due to its pathophysiologic mechanism, which is different from C1-INH, Icatibant is a valuable treatment option in two of our patients in whom pasteurized pd C1-INH concentrate cannot be applied: one patient with a known allergy to pd C1-INH concentrate and one patient with acquired angioedema non-responsive to pd C1-INH concentrate due to high anti-C1-INH antibody titers. This evidence concerns the gene SERPING1 and Allergy.