Home » Articles » Details » Classic: There is no relationship between shellfish, seafood, iodine, and CT contrast allergy

crabCT scans using intravenous (IV) contrast or dye are common tests in medicine. In late 2010, experts reviewed the myth that those who are allergic to seafood are allergic to iodine and cannot have CT scans using contrast. Researchers, in November issue of the Journal of Emergency Medicine, looked at all prior literature regarding rates of contrast reactions and iodine, shellfish or seafood allergy. The found the following facts:

  • No one is allergic to iodine. Iodine is found in everyone’s body within their thyroid gland, within proteins, and within many tissues (e.g. breast). Without iodine, no one can live.
  • Allergies to shellfish and seafood are due to proteins within their muscles and not iodine.
  • Reactions to IV contrast are due to substances within the contrast and not iodine.
  • Prior mild reaction to IV contrast do not increase the risk of severe reactions.
  • Severe reactions to IV contrast are not associated with allergy to seafood, shellfish, or iodine.
  • Anyone who is allergic to one substance (food, medicine) is slightly more likely to be allergic to any other substance like IV contrast. However, even in those allergic to shellfish, the risk of a severe reaction to IV contrast is much less than 1%.
  • Reactions to cleaning solutions, Betadine and Povidine, are not due to iodine and do not mean that you cannot receive IV contrast.

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