Iodinated contrast agents (ICAs) are broadly used in radiology. Frequency of adverse events, including hyperreactivity reactions, noted after their application grows in correlation with the steady increase in the numbers of radio-diagnostic tests performed. Hyperreactivity reactions occur most frequently with the use of ionic ICAs; much rarer with non-ionic ones. Clinical manifestations of hyperreactivity reactions to ICAs involve two groups of symptomatologically typical reactions: immediate and non-immediate (occurring < 60 minutes and > 60 minutes after ICAs’ application). The main risk factors of the occurrence and severity of these reactions are: the previous history of such reactions, poorly controlled asthma, and clonal mast cell activation diseases. Diagnosis of sensitivity to ICAs shares the same procedures and tests used in diagnosing other allergies. The more time passes since the manifestation of sensitivity, the less reliable the diagnostic test is. The predictive value of both positive and negative diagnostic results is limited. In patients with a history of sensitivity reactions to ICAs, before any subsequent radiological test, premedication (antihistamine drugs and steroids) is recommended. This, however, does not guarantee full security, especially in patients with a history of anaphylaxis following the use of ICAs.