By Ian Fagan, MD. I was recently vacationing on a cruise ship. As anybody who regularly cruises most certainly knows, you make your money back not in the casino, but rather on lobster night—a meal consisting of endless portions of delicious, succulent lobster tail. A table mate of mine did not order the lobster. As our conversation continued, she reported that in all her many years eating lobster, she never had a reaction.
People who are allergic to scaled fish are typically allergic to a different muscle protein, parvalbumin. Iodine is not an allergen.Dec 02, · While shellfish allergy is a very real allergy and potentially life threatening, it is not an iodine allergy. The major allergens in shellfish are tropomyosins, which are proteins is the muscle and definitely not cgys.chic-brow.ru: Jennifer Gunter, MD. A misconception about seafood allergy and its relation to radiocontrast media reactions continues to be pervasive among both the medical community and the public at large. The precise origins of the misconception are not entirely known, but the basic notion itself can be traced back more than 30 cgys.chic-brow.ru by: Bottom Line: The risk of seafood allergy being a risk factor for radiocontrast allergy is about the same as having any type of allergy, atopy, and/or prior contrast reactions, compared to the general population, in patients receiving high-osmolar contrast media. Studies of Risk Factors for Radiocontrast Allergy to Low-Osmolar Contrast Media (LOCM).
We all have iodine in our bodies. It is in our thyroid hormones and in amino acids.
I have a shellfish allergy. Can I have contrast?
We would die without iodine. Iodine deficiency is such a potential health problem that most table salt in the United States mevia iodine. Listing iodine as an allergen in the chart is wrong. It is worth repeating, iodine cannot be an allergen.
People can have reactions to providone-iodine prep which contains iodinebut this is predic to allergens in the solution not the iodine. If someone has a reaction to providone-iodine prep the prep should be listed as the allergen, not the iodine. People can have severe reactions to radiocontrast, but these are not allergic reactions. Anaphylaxis is due to a the immune system producing IgE immunoglobulins in response to an allergen, such as the tropomyosin in shellfish.
It is an allergic response.
When a person is re-exposed, the allergen-IgE complex triggers the severe inflammatory cascade. Reactions to radiocontrast are believed to be anaphylactoid and so are not caused by IgE. Anaphylaxis requires IgE to trigger the predit cascade and with an anaphylactoid reaction the substance directly stimulates the inflammatory cascade, no immune system intervention is needed.
As expected, anaphylactoid reactions are much less frequent with the lower osmolar radiocontrast solutions more commonly used today. When incorrect allergies are listed in the chart it breeds confusion and both patients and their providers need and deserve accurate health information.
Authors and Disclosures
Jen Gunter. Tagged as: Radiology. Physician Speaking by KevinMD is the only physician-run, all-physician speakers bureau. Your audience deserves the best. Learn more.
Comments are moderated before they are published. Please read the comment policy. I have a shellfish allergy. Can I have contrast?
For one, iodine cannot be an allergen allerhy it is found throughout the body within thyroid hormone as well as in shellfsih amino acids. Secondly, as described by Leung et al , proteins involved with muscle contraction known as tropomysins, are actually responsible for allergic reactions to shellfish, not the iodine component.
Furthermore, there is no similarity between the structure of tropomysin and that of radiocontrast media itself to suggest that there could be cross-reactivity between them. Putting this all together, not only is there no evidence to support the association between shellfish allergy and contrast reaction, but the difference in shellifsh between the two makes any cross-reactivity exceedingly unlikely.
Physicians should not think twice about a contrast-enhanced CT scan in a patient with a shellfish allergy.
In fact, even obtaining a history of seafood allergy serves to further propagate the myth among these patients.
Lastly, and possibly most importantly, lobster is delicious. Advising people to remove shellfish from their diet without an allergy test to back it up is just plain wrong. The purported link between shellfish allergy and radiocontrast media is indeed mythical.
Pretreatment regimens should be based on a prior history of a contrast-mediated reaction or other high-risk comorbid conditions such as poorly controlled asthma. Commentary by: Tania Elliott, MD Division of Allergy and Immunology The purported link between shellfish allergy and radiocontrast media is indeed mythical.
Intravenous Radiocontrast Media: A Review of Allergic Reactions
Adverse reactions to intravascularly administered contrast media. A comprehensive study based on a prospective survey. Huang SW. Seafood and iodine: an analysis of a medical myth.
Shellfish Allergy Doesn't Predict Reaction to Imaging Agents
Allergy Asthma Proc. Seafood allergy and radiocontrast media: are physicians propagating a myth?A misconception about seafood allergy and its relation to radiocontrast media reactions continues to be pervasive among both the medical community and the public at large. The precise origins of the misconception are not entirely known, but the basic notion itself can be traced back more than 30 cgys.chic-brow.ru by: Nov 01, · Shellfish Allergy Doesn't Predict Reaction to Imaging Agents. The vast majority of reactions are mild to moderate in nature. Patients with allergies are 2 to 3 times more likely to have a reaction to imaging agents than those with without allergy, said Joelle Borhart, MD, from Georgetown University in Washington, DC. Jan 13, · Many believe that since iodine is in both seafood and contrast media, and since many people with the common shellfish allergy had similar reactions after contrast administration, iodine must be the allergen.
Am J Med ; 2 Seafood allergy: tropomyosins and beyond. J Microbiol Immunol Infect ;32 3 — Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med.