Longman Dictionary of Contemporary English
The Collaborative International Dictionary
anaphylaxis \anaphylaxis\ n.
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[Gr. 'ana` back, way from + fy`laxis security, protection.]
1. (Med.) hypersensitivity (to a protein or drug) resulting from prior contact with a substance.
(Med.) an immediate but transient allergic reaction to an antigenic substance to which a person has become hypersensitized; it is characterized by the contraction of smooth muscle and capillary dilation. These reactions are caused by the release of certain substances such as histamine, bradykinin, serotonin, and slow-reacting substance in response to the reaction of the antigen with a mast cell-fixed antibody, chiefly IgE. This term is sometimes used to refer to the severe form of the reaction called anaphylactic shock.
--[Stedman]
anaphylactic shock \anaphylactic shock\ n. (Med.)
a severe form of physiological shock, often having a fatal
outcome, caused by an extreme immunological reaction to
antigens. It is a severe form of anaphylaxis[2], and is
characterized by smooth muscle contraction and capillary
dilation throughout the body, initiated by antibodies of the
IgE class. It is usually seen when an antigen to which a
person has become hypersensitized is injected intravenously
or subcutaneously. It is also called generalyzed
anaphylaxis or systemic anaphylaxis, and sometimes
anaphylaxis.
--[Stedman]
Wiktionary
n. A severe and rapid systemic allergic reaction to an allergen, constricting the trachea and preventing breathing.
WordNet
n. a severe and rapid and sometimes fatal hypersensitivity reaction to a substance (especially a vaccine or penicillin or shellfish or insect venom) to which the organism has become sensitized by previous exposure
Usage examples of "anaphylactic shock".
Woking had died of anaphylactic shock on a Syndicate base that Fleet HQ swore the Headhunters had never seen.
Now Paula was three years dead, dead of anaphylactic shock from a bee sting, if you can believe it.
An unsuspecting patron had died of anaphylactic shock at the table after a single bite.
The kid went into anaphylactic shock in an allergic reaction to fast- penta.
He had gone into some kind of anaphylactic shock and there was no way he could have got himself upstairs, shed his clothes and climbed into bed.
Either the man had sucked spores in through his mouth, or he'd gone into anaphylactic shock from mere skin contact.
I-Five's warning had saved him from days of excruciating pain, if not possible anaphylactic shock and death.