Rare delayed hypersensitivity reactions to contrast media: Severe cutaneous adverse reactions.

The risk of developing a severe delayed cutaneous reaction (SCAR) is very low following iodine-based contrast medium (ICM) administration and extremely low following gadolinium-based contrast agent (GBCA) administration. However, SCAR can be very severe and potentially life-threatening. It is crucial for the imaging physician to recognize danger signals: bullous skin eruption, skin erosion and detachment, mucosal involvement, systemic symptoms, and laboratory abnormalities. Patients suspected of having a SCAR should be urgently referred to a drug allergy specialist or dermatologist. To prevent recurrence, consider exploring alternative imaging modalities and avoid administering the same type of contrast medium involved: if the culprit is a ICM, avoid all ICM and if the culprit is a GBCA, avoid all GBCA. In an allergy centre with experience in SCAR evaluation a careful allergologic analysis may be performed safely several months after the patient has recovered from SCAR. However, allergologic analysis is challenging due to the lack of reliable in vitro diagnostic tests and the risks of in vivo diagnostic tests, particularly drug provocation tests.