The use of iodinated contrast agents (IC) has become common practice nowadays in the daily diagnostic and therapeutic procedures in radiology. Immediate hypersensitivity reactions occurring up to the first hour after injection of IC, can be of serious consequences, occasionally leading to death. This justifies the establishment of a prevention algorithm, including a sharp identification of those at risk and the implementation of premedication with corticosteroids. A history of previous reaction to IC is the major risk factor of a new reaction. Other risk factors include asthma, atopy and cardiomyopathy. The factors that influence the severity of the hypersensitivity allergic reactions are female gender, age, and taking beta blockers or ACE inhibitor drugs.