Diagnostic agents

Hypersensitivity to diagnostic agents may be caused by allergic and nonallergic mechanisms. Immediate hypersensitivity reactions (IHRs) with anaphylaxis are common to iodinated radiocontrast media (RCM), gadolinium-based contrast agents, and blue dyes. In some patients, an immediate-type allergy can be demonstrated by skin test and basophil activation test. Drug provocation tests can be done to confirm tolerability of skin test-negative alternatives. Non-immediate hypersensitivity reactions (NIHRs) to RCM present with exanthemas and are mostly skin test-positive T-cell-mediated hypersensitivity reactions.