What Seafood and Contrast Dye Allergies Have in Common

Are you allergic to seafood? If so, then you may be concerned about having a Computed Tomography (commonly referred to as CT) scan done. This procedure often uses a contrast dye that can trigger a dangerous immune system response in some people.

The Basics about CT Scans

If you've ever had a CT scan performed, you know that this is a diagnostic screening tool that uses a computer-enhanced machine to analyze two-dimensional photos of your body. As part of this procedure, sometimes a contrast dye is used to make the pictures easier to read. However, this dye can contain some iodone, which has been found to cause allergic reactions, and some people with seafood worry that they're at increased likelihood for such negative effects.

The Seafood Connection

While people with seafood allergies may indeed be vulnerable to the effects of a contrast dye allergy, you may be surprised to know that they don't have exclusive rights to this concern. In fact, a number of research studies have determined that the same can be said of people with any type of allergy or asthma.

Further complicating the situation is that it's almost impossible to predict which patients will have the reaction. This is because some patients experience a dangerous contrast dye allergy reaction at even the smallest test exposure, while other people won't react to a trial run of the contrast dye, yet will go on to have a dangerous allergic response to the full dosage.  So there's no way to know up front when it's safe to proceed with the CT scan, and when proceeding will put a patient at risk.

Be Prepared

If you're worried about having a CT scan done with contrast dye, the best way to protect yourself is to make sure any technicians you work with know that you have allergies and can recognize and respond to the earliest signs if you should experience any problems. The truth is that such a reaction is actually extremely rare, but it does happen.

Some people also believe that sensitivity to shellfish increases your risks. Actually, doctors now say that shellfish allergies aren't specifically related to causing a contrast dye allergy. However, people with multiple food allergies and asthma can be at higher risk.

If you fall into the higher risk group, or if you've had a contrast dye allergy in the past, it can be helpful to talk to your doctor to determine whether you should steer clear of this entirely or whether taking an antihistamine and steroid preventatively can provide a protective effect.


Canadian Journal of Emergency Medicine


Medical Imaging Services (Oak Lawn, Ill.)

University of Rochester Medical Center