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Drug allergy: Pathogenesis

Werner J Pichler, MD
Section Editor
N Franklin Adkinson, Jr, MD
Deputy Editor
Anna M Feldweg, MD


A drug allergy is an adverse drug reaction that results from stimulation of the immune system by a medication. The pathogenesis of different types of drug-allergic reactions will be reviewed here. The classification and clinical features of drug-allergic reactions are discussed elsewhere. (See "Drug allergy: Classification and clinical features".)


Drugs can elicit drug-specific immune responses in two ways (table 1):

The drug may act as an antigen and elicit one of several classic immune responses.

The drug may directly interact with immune receptors, and under certain circumstances, lead to activation of specific immune cells.

Drugs acting as antigens — Most medications are small molecular weight compounds with simple chemical structures which are not easily recognized by immune cells and are considered too small to interact with immune receptors with sufficient strength to activate T or B cells. Thus, most drugs are not effective antigens and are not immunogenic in their native state.


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Literature review current through: Sep 2016. | This topic last updated: Jul 30, 2015.
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