Anaphylaxis is a source of anxiety for patients and healthcare providers. It is a medical emergency that presents with a broad array of symptoms and signs, many of which can be deceptively similar to other diseases such as myocardial infarction, asthma, or panic attacks. In addition to these diagnostic challenges, anaphylaxis presents management difficulties due to rapid onset and progression, lack of appropriate self-treatment education and implementation by patients, severity of the allergic response, exacerbating medications or concurrent disease, and unpredictability. The most common causes of anaphylaxis are food allergies, stinging insects and immunotherapy (allergy shots) but idiopathic anaphylaxis, latex allergy and drug hypersensitive all contribute to the epidemiology. Reactions to IVP and other dyes are coined anaphylactoid reactions but have identical pathophysiology and treatment, once the mast cell has been degranulated. As many antigens can be the trigger for fatal anaphylaxis, it is useful to examine the features of each etiology individually, highlighting factors common to all fatal anaphylaxis and some specific to certain etiologies. Generally what distinguishes a fatal from non fatal reaction is often just the rapidity to apply correct therapy. Prevention is clearly the key and should identify high-risk patients in an attempt to minimize the likely of a severe reaction. Although fatal anaphylaxis is rare, it is likely underreported.