n. A sudden, usually systemic allergic reaction, characterized by vasodilation resulting in decreased blood pressure, smooth muscle contraction resulting in shortness of breath, and hives, caused by hypersensitivity induced by a secondary exposure to a foreign substance, such as a drug or protein, after an initial sensitizing exposure. [ANA- + (PRO)PHYLAXIS.] an′a·phy·lactic (-lăktĭk), an′a·phy·lactoid (-toid) adj. an′a·phy·lacti·cal·ly adv. |
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