Anaphylactic shock

Pathology. a severe and sometimes fatal allergic reaction to a foreign substance, especially a protein, as serum or bee venom, to which an individual has become sensitized, often involving rapid swelling, acute respiratory distress, and collapse of circulation.
noun
a severe, sometimes fatal, reaction to a substance to which a person has an extreme sensitivity, often involving respiratory difficulty and circulation failure

anaphylactic shock n.
A severe, sometimes fatal allergic reaction characterized by a sharp drop in blood pressure, urticaria, and breathing difficulties that is caused by exposure to a foreign substance, such as a drug or bee venom, after preliminary or sensitizing exposure. Also called anaphylaxis.
anaphylactic shock
(ān’ə-fə-lāk’tĭk)
A sudden, life-threatening allergic reaction, characterized by dilation of blood vessels with a sharp drop in blood pressure and bronchial spasm with shortness of breath. Anaphylactic shock is caused by exposure to a foreign substance, such as a drug or bee venom, to which the individual has been previously exposed. The substances act as antigens, provoking a preliminary immune response during the first exposure that results in a full-blown, immediate response during secondary exposure, called an immediate hypersensitivity reaction. Emergency treatment, including epinephrine injections, must be administered to prevent death. Also called anaphylaxis.