Can a person be allergic to carotid angiogram dye?

Yes. A person can be allergic to iodinated contrast material just like any other substance. The allergic response can vary from minimal to severe. Regardless of the severity, once you have an allergic response you are at risk for the some or worse if exposed to the dye again. Always notify your doctor of any allergies.
Yes. If any question notify your doctor or notify technologist before your test. Can be serious. Can give medication to help prevent reactions.