Side effects of contrast media can be categorized into 2 types, idiosyncratic reactions, physical and chemical reactions. 1. Atopic reaction: mainly due to its own characteristics, not related to the dose, the common symptoms that can occur are skin itching, angioedema, nausea and vomiting, urticaria, conjunctival congestion, respiratory distress, shock, bronchospasm, death and so on. 2. Physical and chemical reactions: related to the ionic concentration and osmotic pressure of the contrast agent, those with high osmotic pressure may have pain, decreased blood pressure, vasodilatation, etc.; the toxicity of ionic type, especially to the nervous system, is much higher than that of non-ionic type. Close observation is needed during contrast, and once side effects occur, the injection should be stopped immediately or appropriate treatment measures should be taken in time to prevent life-threatening effects.