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. Contrast Dye Shellfish Allergy Reactions to radiocontrast media and its managment – than nonatopic individuals to have a severe adverse reaction to intravenous iodinated contrast media. Iodine is not an allergen. Seafood allergy and radiocontrast media: are physicians propagating a myth? A ventilation‐perfusion scan reveals heterogeneous perfusion defects consistent with an intermediate probability (20%80%) for pulmonary embolism. Shellfish allergy has nothing to do with iodine or contrast. Do you think this is a low‐value practice? Four types of hypersensitivity reactions have been described (type IIV)[3]; allergic reactions mediated by immunoglobulin E (IgE) represent type I hypersensitivity reactions. Should a history of shellfish allergy affect decision making regarding whether to administer IV contrast?WHY YOU MIGHT THINK ASKING ABOUT SHELLFISH ALLERGIES BEFORE PERFORMING CONTRAST‐ENHANCED CT SCANS IS HELPFULFish and shellfish contain iodine, and allergic reactions to seafood are quite common, with a prevalence ranging anywhere between 2% and 6% of the population. 2008 Aug;121(8):e19. Anaphylactoid reactions to contrast differ from anaphylactic reactions as follows. Patients with seafood and other food allergies do not require premedication prior to CT scans. 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. Iodine Allergy. We invite you to be part of that discussion. The following are some examples: Allergy: Patients who have had a prior allergic-like reaction or unknown-type reaction (i.e., a reaction of unknown manifestation) to contrast medium have an approximately 5-fold increased risk of developing a future allergic-like reaction if exposed to the same class of contrast medium again [3]. So there’s no direct relationship between shellfish and contrast allergies. Conclusions: Epub 2017 Oct 24. [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. [10] Using their results, we compared the frequency of reactions in patients with histories of seafood allergy (6.3%, 4/64) to patients with any other type of allergy or atopic state (9.2%, 212/2304) and found no statistically significant differences (P = 0.418). 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. It may cause a rash in sensitive people. In 1 study, nearly 92% of patients presenting to a pediatrics clinic with a suspected seafood or shellfish allergy cited iodine as the culprit. Share what you do in your practice and join in the conversation online by retweeting it on Twitter (#TWDFNR) and liking It on Facebook. doi: 10.2500/aap.2018.39.4160. 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. There is no reason for providers and support staff to specifically inquire about seafood allergies. [8] Patients with a history of atopy, asthma, and food allergies (including seafood) are at approximately 2 to 3 times greater risk of contrast reactions.[9]. Tropomyosins cross react among various shellfish, but not scaled fish so that is why you can be allergic to crab and eat salmon. We invite you to propose ideas for other Things We Do for No Reason topics by emailing [email protected], Copyright © by Society of Hospital Medicine or related companies. [8] Patients with a history of atopy, asthma, and food allergies (including seafood) are at approximately 2 to 3 times greater risk of contrast reactions. Both authors independently performed literature reviews, including position statements of stakeholder organizations, to gain perspective on important issues. Instead, fish and shellfish contain proteins (parvalbumin and tropomyosins, respectively), which act as the major allergens, not iodine. Gadavist (gadobutrol) is a contrast agent that has magnetic properties. However, both physicians and patients misunderstand the role that allergies play in reactions to radiocontrast media, especially with regards to shellfish and iodine. 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. You can be allergic to all types of shellfish or only to mollusks (clams, mussels, oysters and scallops as well as limpets, periwinkles, snails [escargot]… Even, those, who have an allergy to iodine cleaners that are used on the skin, may not be at risk of getting an allergy from iodine contrast. Soon after the injection, the patient went into anaphylactic shock on the CT table. [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. However, much of this risk may be borne by the subgroup with asthma since few studies have evaluated those with atopic disease, but without asthma. However, people with multiple food allergies and asthma can be at higher risk. It is used widely in the United States for radiological studies such as angiograms, X-rays, magnetic resonance imaging (MRI), and computed tomography (CT) scans. Reactions to IV contrast are likely related to some component of the contrast media instead of the iodine itself. [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. These reactions are not related to or mediated by IgE antibodies and do not require prior exposure.True classic allergic reactions, on the other hand, are mediated by IgE antibodies in which initial exposure to an allergen (antigen) is followed by subsequent exposure and production of IgE antibodies. [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. [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. Ingested iodine is converted to iodide, the ionized form of iodine, in the gut. Similarly, Shehadi evaluated seafood as well as asthma, hay fever, common medications (eg, penicillin, aspirin, morphine), and others. National Center for Biotechnology Information, Unable to load your collection due to an error, Unable to load your delegates due to an error. Please enable it to take advantage of the complete set of features! Iodine is an essential trace mineral, required for the synthesis of thyroid hormones. Kaufman E, Lagu T, Hannon NS, Sagi J, Rothberg MB. 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. Epub 2015 May 14. compared the frequency of contrast reactions in patients with histories of seafood allergy, food allergy, asthma, hay fever, hives, and contrast medium. A 55‐year‐old patient with a history of chronic obstructive pulmonary disease and diabetes mellitus presented to the emergency room with acute shortness of breath and right leg swelling that began 1 week after lumbar disk surgery. [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). The high concentration of the contrast can shock cells called basophils into releasing their granules filled with histamine. This myth originated in the 1970s from a survey of patients who reported prior reactions to contrast media. [12], 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. True allergies result when your immune cells react to a protein—not a … 2016 Dec;113(12):1023-1028. doi: 10.1007/s00347-016-0359-9. Importantly, patients with a … Allergy unlikely : If you never had a contrast dye study in past, allergy is unlikely. ISSN 1553-5606, Choosing Wisely: Things We Do For No Reason, Department of Radiology, Johns Hopkins University School of Medicine, Department of Medicine and Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, Department of General Internal Medicine, Johns Hopkins Hospital, Baltimore, Maryland. Iodine is essential for thyroid function but can cause an adverse reaction in some people. The primary allergen in shellfish that stimulates allergic reactions is tropomyosin. 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). [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. True classic allergic reactions, on the other hand, are mediated by IgE antibodies in which initial exposure to an allergen (antigen) is followed by subsequent exposure and production of IgE antibodies. 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. ["Iodine allergy" : A medical myth with risks for the ophthalmological patient]. 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. The urologist thought that the patient might have a renal mass and sent him to radiology for a CT scan.  |  Similarly, Shehadi evaluated seafood as well as asthma, hay fever, common medications (eg, penicillin, aspirin, morphine), and others. A review of research studies found a lower rate of reactions to IV contrast in eras in which low‐osmolarity agents were exclusively used (0.2% after 1991) versus eras in which high‐osmolarity agents were exclusively used (7.0% between 1985 and 1986). Although fish and shellfish contain iodine, so too do a wide variety of commonly consumed foods (eg, yogurt, milk, bread). It is a myth that shellfish allergy means it is unsafe to receive iodine dyes. [4]What Causes Reactions to IV Contrast Media?Around the world, tens of millions of injections occur every year for contrast‐enhanced scans. 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. Method: Having a reaction to an iodine-based contrast dye is also not the same as an allergy to seafood, which may be rich in iodine. CT Contrast Agents and Shellfish Allergies. We invite you to be part of that discussion. The purported link between shellfish allergy and radiocontrast media is indeed mythical. Most intravascular contrastmedia are derivatives of tri-iodobenzoic acid. 2018 Feb;14(2):397-404. doi: 10.1016/j.nano.2017.10.004. Westermann-Clark E, Pepper AN, Talreja N, Lockey RF. [13] The American College of Radiology recommends pretreatment with corticosteroids only for those patients who have previously experienced moderate to severe reactions to IV contrast. eCollection 2015. Most people who are allergic to shellfish react to certain proteins these foods contain, not to iodine. A 55‐year‐old patient with a history of chronic obstructive pulmonary disease and diabetes mellitus presented to the emergency room with acute shortness of breath and right leg swelling that began 1 week after lumbar disk surgery. In 1 of the few studies evaluating seafood allergies specifically, Witten et al. In other words, allergic people can react to multiple different things! NIH A patient was referred to urology after having several episodes of gross hematuria. Most contrast allergies are anaphylactoid rather than anaphylactic (see below). [8]WHAT YOU SHOULD DO INSTEAD: ASK ABOUT PRIOR CONTRAST REACTIONS BEFORE ADMINISTERING CONTRASTWhen a patient presents for a contrast‐enhanced CT scan, patients should be asked if they have experienced reactions to contrast and the severity and type of the associated reactions. Anaphylactoid reactions are caused by direct release of histamine into the bloodstream in response to interacting with chemicals. HHS 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? The authors do not have any relevant financial disclosures to report. Debunking myths about "allergy" to radiocontrast media in an academic institution. It is thought that the majority of these reactions are anaphylactoid reactions instead of true classic allergic reactions, given that IgE antibodies are not consistently elevated in patients who exhibit these reactions. Asking specifically about seafood allergies before performing an IV contrast CT scan is a Thing We Do for No Reason. [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. 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. Iodinated contrast media are the most efficientproducts to enhance the visibility of vascular structures and organsduring radiographic procedures. Although all allergies seem to increase the likelihood of having a reaction to contrast, only a history of previous contrast reactions will prompt a change in management. Low osmolality contrast & premedication helps. Shellfish Allergy Iodine Contrast. Severe allergy to iodine contrast and renal insufficiency are two main problems with iodine-based contrast media. To enhance the visibility of vascular structures and organsduring radiographic procedures 14 ( 2 ):397-404. doi:.! 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