In the past, it had been suggested that, because of their high iodine content, the contrast dyes (or agents) might lead to cross-reactions in shellfish-allergic patients. This form of seafood also tends to be high in iodine.
“You can’t be allergic to iodine. It’s already in your body – it’s found in thyroid hormones and amino acids,” says Dr. Joelle Borhart of Georgetown University Hospital in Washington, D.C. “Iodine is essential for our survival.”
Shellfish and Iodine: a Medical Myth
Borhart conducted an analysis of several studies. She found there was no reason to single out those with shellfish allergy as being susceptible to reacting to iodine in imaging agents.
It is unclear how this medical myth started, but it certainly has remained pervasive. One study found that 92 percent of shellfish-allergic patients believed they would react to iodine. Another found that a majority of radiologists still ask patients whether they have that allergy.
Those with shellfish allergy are not allergic to iodine, “but to a muscle protein in the shellfish called tropomyosin,” notes Borhart.
“Overall, radiocontrast material is quite safe. Serious, immediate reactions are very rare, and tend to occur unpredictably,” she says.