Hypersensitivity Reaction
An exaggerated immune response to a drug ranging from mild skin reactions to severe systemic reactions. All injectable peptide drugs carry some risk. Patients with known hypersensitivity to a peptide drug or its excipients should not receive that product.
Technical Context
Gell-Coombs classification: Type I (immediate/IgE-mediated — mast cell degranulation → histamine, leukotrienes → urticaria, angioedema, anaphylaxis; onset minutes to hours), Type II (antibody-mediated cytotoxicity — IgG/IgM against cell-surface antigens → complement activation, ADCC; onset hours to days), Type III (immune complex — drug-antibody complexes deposit in tissues → complement activation, inflammation; onset days to weeks; serum sickness-like reactions), Type IV (delayed/T-cell-mediated — sensitised T cells release cytokines → inflammation; onset 48-72 hours; contact dermatitis). For peptide drugs, Type I reactions (including anaphylaxis) are the most clinically significant acute risk. All injectable peptide drug labels include warnings about hypersensitivity. Skin testing and desensitisation protocols exist for some peptide drugs.