Clinical review| Volume 39, ISSUE 5, P701-707, November 2010

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The Relationship of Radiocontrast, Iodine, and Seafood Allergies: A Medical Myth Exposed


      Background: Radiocontrast agents are some of the most commonly used medications in the emergency department. However, both physicians and patients misunderstand the role that allergies play in reactions to radiocontrast media, especially with regards to shellfish and iodine. Objectives: We sought to review the literature describing rates of contrast reactions and risk of contrast administration to patients with iodine allergy, shellfish or seafood allergies, or prior reactions to intravenous iodinated contrast. Method: Both authors independently performed literature reviews, including position statements of stakeholder organizations, to gain perspective on important issues. They subsequently performed a systematic search for articles that estimated the risk of administration of iodinated contrast to those with a prior history of contrast reaction, “iodine allergy,” or reaction to seafood or shellfish. Results: The risk of reactions to contrast ranges from 0.2–17%, depending on the type of contrast used, the severity of reaction considered, and the prior history of any allergy. The risk of reaction in patients with a seafood allergy is similar to that in patients with other food allergies or asthma. A history of prior reaction to contrast increases the risk of mild reactions to as high as 7–17%, but has not been shown to increase the rate of severe reactions. Severe reactions occur in 0.02–0.5% and deaths in 0.0006–0.006%; neither have been related to “iodine allergy,” seafood allergy, or prior contrast reaction. Low-osmolality contrast media became available in 1988, and many of the higher risk estimates were from the era before it was widely available. Conclusions: Iodine is not an allergen. Atopy, in general, confers an increased risk of reaction to contrast administration, but the risk of contrast administration is low, even in patients with a history of “iodine allergy,” seafood allergy, or prior contrast reaction. Allergies to shellfish, in particular, do not increase the risk of reaction to intravenous contrast any more that of other allergies.


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        • Beaty A.D.
        • Lieberman P.L.
        • Slavin R.G.
        Seafood allergy and radiocontrast media: are physicians propagating a myth?.
        Am J Med. 2008; 121: e1-e4
        • Shehadi W.H.
        Adverse reactions to intravascularly administered contrast media.
        Am J Roentgenol Radium Ther Nucl Med. 1975; 124: 145-152
        • Shehadi W.H.
        • Toniolo G.
        Adverse reactions to contrast media: a report from the committee on safety of contrast media of the international society of radiology.
        Radiology. 1980; 137: 299-302
        • Valls C.
        • Andia E.
        • Sanchez A.
        • Moreno V.
        Selective use of low-osmolality contrast media in computed tomography.
        Eur Radiol. 2003; 13: 2000-2005
        • Kopp A.F.
        • Mortele K.J.
        • Cho Y.D.
        • Palkowitsch P.
        • Bettmann M.A.
        • Claussen C.D.
        Prevalence of acute reactions to iopromide: postmarketing surveillance study of 74,717 patients.
        Acta Radiol. 2008; 49: 902-911
        • Bettmann M.A.
        • Heeren T.
        • Greenfield A.
        • Goudey C.
        Adverse events with radiographic contrast agents: results of the SCVIR contrast agent registry.
        Radiology. 1997; 203: 611-620
        • Katayama H.
        • Tanaka T.
        Clinical survey of adverse reactions to contrast media.
        Invest Radiol. 1988; 23: S88-S89
        • Cochran S.T.
        • Bomyea K.
        • Sayre J.W.
        Trends in adverse events after IV administration of contrast media.
        AJR Am J Roentgenol. 2001; 176: 1385-1388
        • Katayama H.
        • Yamaguchi K.
        • Kozuka T.
        • Takashima T.
        • Seez P.
        • Matsuura K.
        Adverse reactions to ionic and nonionic contrast media.
        Radiology. 1990; 175: 621-628
        • Lasser E.C.
        • Berry C.C.
        • Talner L.B.
        • et al.
        Pretreatment with corticosteroids to alleviate reactions to intravenous contrast material.
        N Engl J Med. 1987; 317: 845-849
        • Witten D.M.
        • Hirsch F.D.
        • Hartman G.W.
        Acute reactions to urographic contrast medium: incidence, clinical characteristics and relationship to history of hypersensitivity states.
        Am J Roentgenol Radium Ther Nucl Med. 1973; 119: 832-840
        • Leung P.S.
        • Chen Y.C.
        • Chu K.H.
        Seafood allergy: tropomyosins and beyond.
        J Microbiol Immunol Infect. 1999; 32: 143-154
        • American College of Radiology
        Manual on contrast media.
        American College of Radiology, Reston, VA2008 (Accessed September 20, 2009)
        • American Academy of Allergy Asthma and Immunology
        The risk of severe allergic reactions from the use of potassium iodide for radiation emergencies.
        American Academy of Allergy Asthma and Immunology, Milwaukee, WI2004 (Accessed September 20, 2009)
        • Food and Drug Administration
        Drug details: Metrizamide (NDA) 017982.
        Food and Drug Administration, Silver Spring, MD2009 (Accessed September 20, 2009)
        • Mishkin M.M.
        Contrast media safety: what do we know and how do we know it?.
        Am J Cardiol. 1990; 66: 34F-36F
        • Lieberman P.L.
        • Seigle R.L.
        Reactions to radiocontrast material. anaphylactoid events in radiology.
        Clin Rev Allergy Immunol. 1999; 17: 469-496
        • Costa N.
        Understanding contrast media.
        J Infus Nurs. 2004; 27: 302-312
        • Roberts J.R.
        Complications of radiographic contrast material: miscellaneous considerations.
        Emerg Med News. 2004; 26: 39-42
        • Tramer M.R.
        • von Elm E.
        • Loubeyre P.
        • Hauser C.
        Pharmacological prevention of serious anaphylactic reactions due to iodinated contrast media: systematic review.
        BMJ. 2006; 333: 675