Nonsteroidal antiinflammatory drugs (NSAIDs), including aspirin (ASA), are associated with an array of adverse effects, ranging from mild gastritis to life-threatening allergic reactions. (See "Nonselective NSAIDs: Overview of adverse effects".)
The ingestion of NSAIDs can give rise to several allergic and "pseudoallergic" reactions, which develop within minutes to hours of administration. Allergic reactions are abnormal immunologic reactions to NSAIDs, while pseudoallergic reactions are nonimmunologic reactions that are believed to result from acquired alterations in the biochemical pathways upon which NSAIDs act.
The prevalence of allergic and pseudoallergic reactions to NSAIDs in the general population is not known. These reactions occur sporadically in both children and adults. Symptoms include rhinoconjunctivitis, bronchospasm, urticaria/angioedema, and anaphylaxis.
In addition to allergic reactions, there are various types of idiosyncratic adverse reactions to NSAIDs/ASA that are presumed or known to involve other types of immune mechanisms. These include, but are not limited to, aseptic meningitis, hypersensitivity pneumonitis, thrombocytopenia, interstitial nephritis, erythema multiforme, fixed drug eruptions, toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema nodosum, maculopapular eruptions, and bullous leukocytoclastic vasculitis . These types of reactions are discussed in various topic reviews. (See "Nonselective NSAIDs: Overview of adverse effects" and "Drug eruptions" and "Stevens-Johnson syndrome and toxic epidermal necrolysis: Pathogenesis, clinical manifestations, and diagnosis".)
The clinical manifestations of allergic and pseudoallergic reactions caused by NSAIDs/ASA will be reviewed here. The challenge protocols used by allergy specialists to evaluate and manage affected patients are presented separately. (See "Diagnostic challenge and desensitization protocols for NSAID reactions".)