A patient receiving a CT scan is typically required to take a contrast dye that makes organs, blood vessels and tissues more noticeable during imaging. Although side effects are typically mild, in rare cases they may be severe.

Mild Side Effects

Mild side effects associated with contrast dye include a warm sensation throughout the body and metallic taste in the mouth from the iodine in the dye. Itching and hives may occur, which can last a few minutes to a few hours.

Serious Side Effects

Serious side effects, although much less likely, may include breathing difficulty, swelling of the throat, or swelling of other parts of the body.


In most situations the benefits of contrast dye outweigh the risks associated with it, although you should let your doctor know if you are allergic to or sensitive to medications, contrast dye, iodine or shellfish.

Potential Danger

MRI contrast dye may be linked to nephrogenic systemic fibrosis (NSF) and nephrogenic fibrosing dermopathy (NFD). Both of these diseases are rare and involve fibrosis of the joints, eyes, skin and internal organs.

Other Uses

Contrast dye is not always necessary for a CT scan, but it must be used to detect the spread of malignancy in the brain or liver. See Resources.