Idiopathic anaphylaxis presents a problem requiring rapid diagnosis and initiation of therapy. Some cases are complex and difficult to assess. We present four cases of unusual complexity to illustrate diagnostic and therapeutic problems. Two cases were found not to be idiopathic anaphylaxis, one being undifferentiated somatoform idiopathic anaphylaxis and the other very severe urticaria. Various conditions can be or mimic idiopathic anaphylaxis, and patience and observation can result in reasonable outcomes.