The myth of iodine allergy
© 2013 Roy Benaroch, MD
One of the goals of this site—along with soliciting donations and letting me write and publish goofy stuff—is to promote good, solid science-based medical information. If you’ve been around, you know I don’t go for made-up-stuff. And I especially don’t like it when it’s other doctors spreading the misinformation.
Have you had a reaction to intravenous contrast dye during a CT scan or other exam? Have you been told you’re allergic to iodine, and that you should avoid seafood?
Wrong wrong wrong. You’re not allergic to iodine. And you can almost certainly have seafood—you’re no more likely than anyone else with any allergy to be allergic to seafood, or salt, or dairy products, or anything else that contains natural or added iodine. The only thing you need to avoid is that same kind of IV contrast dye in the future.
Iodine is a natural element. It is essential for life—if you didn’t have any, your thyroid gland couldn’t work, and you’d get sicker and sicker. Iodine is found especially in seafood, but also in some vegetables and dairy products (especially if the cows were grazing on land where the soil was rich in iodine.) In many countries, including the USA, salt is routinely fortified with iodine to prevent thyroid disease.
Allergies are almost always triggered by proteins—big, honking, complex molecules made of chains of amino acids—or other big molecules. Someone who’s had a reaction to IV contrast dye has not reacted to the iodine, but to the other constituents of the dye. These reactions can be severe or life-threatening, and people who’ve had these reactions need to be careful to make sure a different, low-reaction type of dye is used in the future if they need further studies.
It may be that people who’ve had reactions to IV contrast might also have a food allergy, and that food allergy might even be to seafood. But there is no increased risk of seafood allergy than to allergy to any other foods. You might be allergic to seafood or milk or eggs or peanut or… nothing. But you’re not allergic to iodine. You’re allergic to IV contrast. Got it?