Hi Paula — the official diagnosis was “Idiopathic angioedema.” The idiopathic part means, of course, the docs don’t know what causes it. I didn’t experience the hives, just swelling of my lips and throat, so it was more dangerous than inconvenient. And there is no allergic trigger known — it just seemed to happen. Even in the ER, Prednisone or anti-inflammatory drugs didn’t do much but kick up my blood pressure.