A survey of radiologists and interventional cardiologists revealed that 65.3% and 88.9%, respectively, asked about seafood or shellfish allergies prior to administering contrast enhanced CT scans, and 34.7% and 50.0%, respectively, stated that they would withhold contrast media or recommend premedication with corticosteroid/antihistamines for patients with seafood or shellfish allergy. 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. The major allergens in shellfish are tropomyosins, which are proteins is the muscle and definitely not iodine. So there’s no direct relationship between shellfish and contrast allergies. [6] Overall, the results suggest that patients with seafood allergy are at no higher risk for having a contrast reaction compared with patients with other food allergies or other forms of atopy. Allergies to shellfish, in particular, do not increase the risk of reaction to intravenous contrast any more that of other allergies. For those affected, even a small bite of shrimp, lobster, or crab, can result in … Actually, doctors now say that shellfish allergies aren't specifically related to causing a contrast dye allergy. Iodinated contrast dye can also cause an allergic reaction. Method:  |  Westermann-Clark E, Pepper AN, Talreja N, Lockey RF. Four types of hypersensitivity reactions have been described (type IIV)[3]; allergic reactions mediated by immunoglobulin E (IgE) represent type I hypersensitivity reactions.Although fish and shellfish contain iodine, so too do a wide variety of commonly consumed foods (eg, yogurt, milk, bread). [6] Higher reaction rates were associated with the use of higher‐osmolarity contrast agents. Ingested iodine is converted to iodide, the ionized form of iodine, in the gut. Should a history of shellfish allergy affect decision making regarding whether to administer IV contrast? [8]Allergic‐like, or anaphylactoid, reactions related to contrast are largely thought to have a fundamentally different molecular mechanism than true classic allergic reactions. Low-osmolality contrast media became available in 1988, and many of the higher risk estimates were from the era before it was widely available. [9]Do Shellfish Allergies Place Patients at Higher Risk for Contrast Reactions Than Other Allergies?In 1 of the few studies evaluating seafood allergies specifically, Witten et al. Shellfish allergies are not related to iodinated contrast; the allergan is the shellfish tropomyosin and we therefore do not routinely withold contrast administration in such patients. A patient was referred to urology after having several episodes of gross hematuria. 2016 Dec;23(6):1340-1342. doi: 10.1007/s12350-015-0168-6. Anaphylactoid reactions are caused by direct release of histamine into the bloodstream in response to interacting with chemicals. [6] Overall, the results suggest that patients with seafood allergy are at no higher risk for having a contrast reaction compared with patients with other food allergies or other forms of atopy.Additionally, seafood and other food allergies should be distinguished from food intolerances in which the ingestion of histamine‐rich materials in conjunction with histamine inhibitors (drugs or alcohol) leads to symptoms that can mimic allergic‐like reactions (urticaria, pruritus, diarrhea, asthma). It is used in combination with magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA) to allow blood vessels, organs, and other non-bony tissues to be seen more clearly.  |  Therefore, the resident radiologist told the technologist to proceed with contrast material administration for contrast enhancement. Iodine is not an allergen. Iodine is essential for thyroid function but can cause an adverse reaction in some people. This myth originated in the 1970s from a survey of patients who reported prior reactions to contrast media. 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. [5] Reactions to IV contrast media are not uncommon, occurring anywhere between 0.6% and 17% of the time, with severe reactions occurring between 0.02% and 0.5% of the time. We invite you to be part of that discussion. Although fish and shellfish contain iodine, so too do a wide variety of commonly consumed foods (eg, yogurt, milk, bread). Epub 2013 Jan 9. Seafood and other food allergies do not represent contraindications to obtaining contrast‐enhanced CT scans and should not prompt a change in management.DisclosuresThe authors do not have any relevant financial disclosures to report.Do you think this is a low‐value practice? Contrast dyes create detailed images of blood vessels, tumors and inflammation. Debunking myths about "allergy" to radiocontrast media in an academic institution. Results: [2] As contrast‐enhanced CT scans utilize a variety of iodine‐based agents, patients are often told to avoid CT scans with iodinated contrast agents or receive corticosteroid/antihistamine premedications prior to undergoing CT scans to mitigate potentially life‐threatening allergic reactions. Do you think this is a low‐value practice? Among those patients who risk having an adverse reaction to contrast dye include patients with a history of asthma, cystic fibrosis, shellfish allergy, dehydration or constipation, habitual use of NSAIDs or beta blockers, heart disease, sickle cell, and renal disease. Get the latest public health information from CDC: https://www.coronavirus.gov, Get the latest research information from NIH: https://www.nih.gov/coronavirus, Find NCBI SARS-CoV-2 literature, sequence, and clinical content: https://www.ncbi.nlm.nih.gov/sars-cov-2/. doi: 10.2500/aap.2018.39.4160. Up to 35% of patient will experience a recurrence if no premedication prophylaxis is given. Endophthalmitis following intravitreal anti-vascular endothelial growth factor (VEGF) injection: a comprehensive review. In addition, our bodies contain and require sufficient quantities of iodine for basic functions, making immune reactions to such an essential ingredient of life unlikely. [12]What Do the Guidelines Recommend?For patients who require IV contrast media for CT scans, the American Academy of Allergy, Asthma, and Immunology recommends not routinely ordering lowiso‐osmolar radiocontrast media or pretreating with corticosteroids and antihistamines for patients with a history of seafood allergy. The emergency department team decides against ordering a chest CT scan with contrast to evaluate for a possible pulmonary embolism after noting that the patient's allergies include shellfish, which cause urticaria and facial edema. The authors do not have any relevant financial disclosures to report. Fish and shellfish contain iodine, and allergic reactions to seafood are quite common, with a prevalence ranging anywhere between 2% and 6% of the population. It is a myth that shellfish allergy means it is unsafe to receive iodine dyes. Seafood Allergy And Contrast Dye. Copyright © 2010 Elsevier Inc. All rights reserved. This should hopefully put to rest the myth, that iodine is an allergen and that an allergy to shellfish does not increase the risk of reaction to radiocontrast agents any more than that of having other allergies. [7]Reactions to contrast include allergic‐like reactions as well as a variety of other reactions (eg, arrhythmias, vasovagal reactions, flushing), which are thought to be related to the dose and concentration of contrast media. [1] As a result, patients with suspected shellfish allergies are often told by providers that they are allergic to iodine. Adv Food Nutr Res. There is a common belief that patients who have shellfish allergy cannot have contrast dye when they need CT scans performed. Low osmolality contrast & premedication helps. It is now well established that there is no specific link between shellfish allergy and allergy to contrast agents; there is an increased risk of adverse reactions to contrast agents in patients with any history of allergy . It is not a true allergy but rather an intolerance. 2016 Dec;113(12):1023-1028. doi: 10.1007/s00347-016-0359-9. Severe allergy to iodine contrast and renal insufficiency are two main problems with iodine-based contrast media. These reactions are not related to or mediated by IgE antibodies and do not require prior exposure. [6] Higher reaction rates were associated with the use of higher‐osmolarity contrast agents. Epub 2015 Mar 5. Allergies to shellfish, in particular, do not increase the risk of reaction to intravenous contrast any more that of other allergies. We invite you to be part of that discussion. The method of entry of the contrast dye will vary based on the part of the body that is imaged. Iodine is an essential trace mineral, required for the synthesis of thyroid hormones. Providers and support staff should not ask specifically about shellfish allergies, as they have not been found to be associated with an elevated risk of contrast reactions compared with other allergens. [9] The allergenIgE antibody complex causes the degranulation of mast cells and basophils, leading to the release of histamines.Reactions to IV contrast are likely related to some component of the contrast media instead of the iodine itself. 2013 Apr;24(3):222-6. doi: 10.1016/j.ejim.2012.12.011. Please enable it to take advantage of the complete set of features! In 1 study, nearly 92% of patients presenting to a pediatrics clinic with a suspected seafood or shellfish allergy cited iodine as the culprit. 2008;54:139-77. doi: 10.1016/S1043-4526(07)00004-6. The answer here is clearly yes. Is this truly a Thing We Do for No Reason? Is this truly a Thing We Do for No Reason? Radiocontrast agents are some of the most commonly used medications in the emergency department. Contrast dye may be administered intravenously, orally or rectally. Practices reviewed in the TWDFNR series do not represent black and white conclusions or clinical practice standards, but are meant as a starting place for research and active discussions among hospitalists and patients. Most people who are allergic to shellfish react to certain proteins these foods contain, not to iodine. USA.gov. [8] Nevertheless, the symptoms of these 2 types of reactions (anaphylactoid and allergic reactions) are similar and require comparable treatment to prevent life‐threatening anaphylaxis.What Are the Major Risk Factors for Allergic‐Like Contrast Reactions?Previous studies on risk factors for allergic‐like contrast reactions suggest that the strongest predictor of future contrast reactions is a history of prior contrast reaction (5‐fold higher risk), with an estimated 10% to 35% recurrence risk of contrast reactions. Instead, fish and shellfish contain proteins (parvalbumin and tropomyosins, respectively), which act as the major allergens, not iodine. 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