A skin sensitization test is done before an enhanced CT exam. An enhanced CT requires the use of an iodine-containing contrast agent, and many people are allergic to iodine, so they will have a skin sensitivity test done with the iodine contrast agent before the enhanced CT. Iodine contrast allergy is generally common in people who have had previous food or drug allergies. Some patients with urticaria, asthma, convulsions, pulmonary edema, and heart failure are also more prone to allergic reactions. Special populations such as pregnancy, breastfeeding, pregnancy preparation, etc., should truthfully inform the doctor and ask if there are any contraindications and whether they can do enhanced CT examination. Nowadays, most of the contrast agents are non-ionic, which is safer, and the dosage of contrast agent is lower, the phenomenon of allergy has been gradually decreasing.