Anaphylaxis is a severe form of allergy and in extreme cases can also be fatal. Almost any substance can potentially cause an allergy. If caught early and treatment administered, the outcome is usually good. When in contact with the allergen, body typically reacts severely to the exposure. The reactions can be localized or throughout the entire body. Symptoms of a severe allergic reaction include shock, dyspnea, vomiting, urinary and fecal incontinence. The onset can be quick, often within minutes of exposure to the allergen.