Positive skin tests in late reactions to radiographic contrast media

In the last few years delayed reactions several hours after the injection of radiographic and contrast materials (PRC) have been described with increasing frequency. The authors report two observations on patients with delayed reactions in whom intradermoreactions (IDR) and patch tests to a series of ionic and non ionic PRC were studied. After angiography by the venous route in patient n degree 1 a biphasic reaction with an immediate reaction (dyspnea, loss of consciousness) and delayed macro-papular rash appeared, whilst patient n degree 2 developed a generalised sensation of heat, persistent pain at the site of injection immediately and a generalised macro-papular reaction after 24 hours. The skin tests revealed positive delayed reactions of 24 hours and 48 hours by IDR and patch tests to only some PRC with common chains in their structures. The positive skin tests are in favour of immunological reactions and may help in diagnosis of allergy in the patients.