“Is CT contrast dye dangerous?”

Not nowadays. Used to be.

Contrast is generally considered be safe, though reactions can occur. Most are minor and do not require treatment. Some allergic reactions can be serious and need to be treated with oral or IV drugs. Death can occur very rarely, about 1 in 75000. People with abnormal kidney function can develop worsening of their kidney disease. Those most at risk are elderly with coexisting diseases, have a history of severe allergies or allergy to contrast. Sometimes the IV comes out of the vein and the contrast may be injected into the soft tissues which can cause pain and swelling. The technologist should have you fill out a questionaire to determine if you have any significant risk factors. We do hundreds of contrast studies a day and rarely see a severe reaction.

No. In the old days it was, but not for the past 20 years or so.