Clinical diagnosis of anaphylaxis is based on consideration of the patient's presenting symptoms and signs and on ruling out other sudden-onset multisystem diseases. The differential diagnosis includes common disorders such as acute asthma or acute urticaria [1,2]. It also includes uncommon disorders in which, as in anaphylaxis, delay in making an accurate diagnosis and initiating appropriate treatment can lead to death. As an example, in fatal attacks of hereditary angioedema due to C1-esterase inhibitor deficiency, the predyspneic phase lasts 3.7 h (range 0-11); however, the dyspneic phase lasts only 41 min (range 2-240) and the loss of consciousness phase lasts only 8.9 min (range 0-20) [47].