Iodide contrast agents are commonly used clinically for imaging examinations. In some patients with iodine allergy, iodine contrast agents injected into the body may produce an allergic reaction, so an iodine allergy test is required before imaging. There are various methods of iodine allergy test, including intravenous injection, intradermal test, conjunctival test, oral method, etc. 1. Intravenous injection: Before doing full abdominal or chest enhancement CT, place the catheter for intravenous injection, push 1-2 mL of the original solution on the intravenous catheter, observe for 10-20 minutes, if there are no uncomfortable symptoms, including itching, local redness, obvious discomfort, etc., it can be judged as negative. If there is obvious discomfort, skin itching, shock, blood pressure drop, it is judged as positive; 2. Intradermal test: usually the original solution is diluted, the diluted solution is injected into the skin, observe 10-20 minutes, no redness and swelling performance around the skin is judged as negative. If after injection, there is obvious itching and discomfort, redness and swelling around, it is judged as positive; 3, conjunctival test: 1-2 drops of the original solution on the conjunctiva, observe for about 5 minutes. If there is eye discomfort, conjunctival congestion and edema, it can be judged as positive. If there is no discomfort of allergy, it can be judged as negative. 4. Oral method: Before the contrast examination, 5mL of potassium iodide solution can be taken orally every day for three days to observe whether the body will produce adverse reactions, such as mouth numbness, dizziness, panic, nausea, vomiting, urticaria and other manifestations. If the body does not produce adverse reactions, the test result is negative and further tests can be performed. However, if the body produces an adverse reaction, the test result is positive and the contrast test cannot be performed.