Allergy Myth: Iodine, Shellfish, and IV contrast

Enough already with this nonsense.

Schabelman & Witting. The Relationship of Radiocontrast, Iodine, and Seafood Allergies: A Medical Myth Exposed. The Journal of Emergency Medicine, 2010 39:5 701-707.


The evidence suggests that asking if patients are allergic to shellfish or iodine has no relevance to radiocontrast allergies. This questioning perpetuates the myth of an association between shellfish, iodine, and contrast agents. Instead, ask if they have any allergies, have had a previous reaction to a contrast agent, or have evidence of atopy, such as asthma. Educate nurses and technicians to stop propagating this myth as well.

If your patient offers an allergy to iodine or shellfish, ask the patient if they mean to say that they have had a reaction to intravenous contrast in the past. Educate them that they do not have an “allergy” to iodine, and that an allergy to shellfish does not change the risk of reaction to intravenous contrast any more than any other allergy.

If your hospital does not routinely use a low osmolarity, non-ionic agent, request this type of medium for atopic patients, patients who had a reaction to an intravenous contrast agent in the past, and patients with systemic disease that increases their risk for contrast reaction.

Do not delay emergent studies for steroid premedication. Only lengthy 12h premedication protocols have shown any effect on reaction rates, and this small benefit was manifested primarily by decreasing minor reactions. No steroid protocol has shown a significant benefit in decreasing severe or fatal reactions.

Monitor all patients for at least 20 min after administration of radiocontrast.

Treat any severe reaction to radiocontrast the same way you would treat a severe anaphylactic reaction.

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Also, while we’re on the topic of iodine, have you noticed that on the chlorhexidine packages it says don’t use for lumbar puncture? More nonsense.