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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 [1].

Some drugs can bind directly to effector cells of the immune system (eg, mast cells) and cause mast cell degranulation with the clinical symptoms of urticaria or anaphylaxis [2]. Such symptoms are very similar to some drug-allergic reactions (immunoglobulin E [IgE]) and are called pseudoallergic or nonallergic hypersensitivity reactions. They do not involve drug-specific antibodies or T cells and are thus not truly immune-mediated reactions. Common examples include most reactions to nonsteroidal anti-inflammatory drugs (NSAIDs) and radiocontrast agents, which are discussed elsewhere (See "NSAIDs (including aspirin): Allergic and pseudoallergic reactions" and "Immediate hypersensitivity reactions to radiocontrast media: Clinical manifestations, diagnosis, and treatment".)

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Literature review current through: Nov 2017. | This topic last updated: Sep 18, 2017.
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