The angiotensin-converting enzyme normally helps in conversion of angiotensin I to angiotensin II, which acts as a vasoconstrictor in case of hypovolemia. In addition to that, ACE also helps in the breakdown of bradykinin. When ACE inhibitors (captopril) are given, it inhibits ACE and in addition inhibits the breakdown of bradykinin also, which leads to accumulation of bradykinin level in the body. This increased level of bradykinin presents with a Dry cough, rashes, urticaria and angioedema.