Significant activation of the bradykinin-forming cascade is not obvious in allergic rhinitis, sinusitis, asthma, or even urticaria and angioedema most likely because the amount of mast cell heparin released is limited to the organ involved although one study reports the presence of cleaved high molecular weight kininogen (HK) in chronic spontaneous urticaria (17) indicative of plasma kallikrein formation and release of bradykinin. This evidence concerns the gene KNG1 and urticaria.