DIAGNOSTIC STRATEGIES FOR CONTRAST MEDIA HYPERSENSITIVITY IN RADIOLOGY PRACTICE

Iodinated contrast media (ICM) and gadolinium-based contrast agents (GBCA) support most contrast-enhanced imaging, and modern agents carry a low risk of adverse reactions. Hypersensitivity reactions (HSRs) still occur and range from mild urticaria to fatal anaphylaxis. Clinicians classify HSRs as immediate (IHRs, onset within 1 hour) or non-immediate (NIHRs, later onset, most often after 1 to 3 days). IHRs arise through IgE-mediated or non-IgE mechanisms, while NIHRs reflect T-cell-mediated hypersensitivity and present as maculopapular exanthem or, in rare cases, severe cutaneous adverse reactions. Unverified “iodine allergy” labels and reliance on premedication expose patients to suboptimal imaging and breakthrough reactions. This narrative review synthesizes 12 publications from 2021 to 2025 on the diagnosis of ICM and GBCA hypersensitivity. Skin prick and intradermal tests (IDT) form the core of the work-up, and pooled positivity reaches 52% after severe IHRs. A pooled analysis of 1,137 patients found that IDT up to undiluted ICM raised sensitivity from 0.282 to 0.774 with no loss of specificity. Patch tests and delayed-reading IDT identified the culprit in 47.6% to 85% of patients in recent NIHR cohorts. Basophil activation tests add diagnostic yield after severe IHRs, while lymphocyte-based assays remain research tools. Drug provocation tests confirm tolerance of a skin-test-negative alternative, and a negative test predicts tolerance in more than 90% of re-exposures. Switching to a skin-test-negative agent outperforms premedication with the culprit agent. We propose a four-step diagnostic pathway for adults and children.