Emergencies during phlebology procedures are rare. Nonetheless, a phlebologist needs to be prepared to manage such a situation (like syncope due to anaphylaxis) if it occurs, to distinguish a true emergency from a more benign scenario (like vasovagal syncope), and even to manage an emergency unrelated causally to the procedure itself (like a heart dysrhythmia which happens to occur during sclerotherapy). The focus of such preparations should be actions and information which affect patient outcomes. Physician mental and even medical team rehearsal of such scenarios can improve phlebologist and team responses. This article discusses the differential diagnosis and management of the patient with syncope in a phlebology practice, with emphasis on anaphylaxis.