ABSTRACT

HYPERSENSITIVITY REACTIONS A hypersensitivity reaction (HSR) is an immune-mediated response to a drug or other substance that can result in harm. It is estimated that HSRs account for approximately 5%–10% of all drug-related adverse events. A HSR may occur only once or may recur throughout life following sensitization to a particular antigen. Four basic types of classical immune-mediated hypersensitivity have been described (Table 19.1).