multisystem reaction involving the respiratory, cardiovascular, dermatologic, and gastrointestinal systems Anaphylactic reactions classically involve an IgE-mediated response that occurs after reexposure to an antigen to which the patient has been sensitized The term anaphylactoid reaction is sometimes used to refer to a clinically similar non–IgE-mediated reaction that doesn’t require prior antigen exposure Although the mortality rate for children