Thursday, 29 December 2011

Top Allergy Myths: There is no such thing as an Iodine Allergy-

plate of oysters

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Myth: Iodine Allergy is a Myth - Example: People Who Are Allergic to Shellfish Are Not Actually Allergic to the Iodine in the Shellfish, rather research indicates its the muscle protein.

Some people who are allergic to seafood avoid certain skin medications and diagnostic medical tests that use iodinebecause they fear an allergic reaction. But there is no connection between allergies to fish and shellfish and allergies to iodine. Allergies to fish and shellfish are caused by the protein in them, not the iodine.


Research Paper Debunks the Myth

The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed.

Source

Department of Emergency Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.


"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."

Copyright © 2010 Elsevier Inc. All rights reserved.






June 2010 · Vol. 59, No. 06: 314

LETTERS

Shellfish-iodine nexus is a myth

I read with interest the Florida case with the $4.7 million verdict (Iodine contrast media kills man with known shellfish allergy, What’s the Verdict? J Fam Pract. 2010;59:244). As a dermatologist who deals with many allergy issues, I was surprised that the verdict was based on the “supposed” cross-reaction of a shellfish allergy with contrast iodine material. Unfortunately, this is a medical myth that has been propagated for many years.

An excellent review on this subject recently appeared in the Journal of Emergency Medicine.1 The authors surveyed 231 physicians at 6 academic medical centers and found that 89% of cardiologists and two-thirds of radiologists routinely ask their patients if they are allergic to shellfish before administering an iodinated contrast agent. They also noted that 35% of radiologists and 50% of cardiologists would withhold radiocontrast or premedicate patients with shellfish allergies.

When an individual has a seafood or shellfish allergy, it is the protein in the animal that the individual is allergic to. The allergens from fish and shellfish are actually 2 different types of proteins, and have absolutely nothing to do with iodine. Iodine is an essential element that is found throughout the body and is essential to the production of thyroid hormone and various amino acids in the body. One could not survive without iodine. It is, therefore, impossible to have a true allergy to iodine. Although an individual could react to the various allergens contained in iodine skin preps, it is not the iodine that is causing the allergy.

It is the general opinion of experts in the fields of radiology and allergy/immunology that any “allergic” individual has a 3-fold increase in the likelihood of an allergic reaction to radiocontrast material, and more than 55% of individuals have at least 1 or 2 allergies. It is not reasonable to withhold needed treatment, whether it be contrast dye, anesthesia, or any medication, for fear of a potential reaction—particularly in an emergency like the case in question, in which the procedure was done in an attempt to save the life of a 41-year-old patient. The risk of dying from cardiac arrest is great, while the risk of death from contrast dye is miniscule.

Propagating the myth of the seafood-iodine-contrast material connection not only disseminates misinformation, but also breeds multimillion dollar lawsuits.

Melinda F. Greenfield, DO
Albany, Ga

  1. Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med. 2009; Dec. 31 [E pub ahead of print].

1 comment:

  1. J Emerg Med. 2010 Nov;39(5):701-7. Epub 2010 Jan 4.
    The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed.
    Schabelman E, Witting M.
    Source
    Department of Emergency Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
    Abstract
    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.
    Copyright © 2010 Elsevier Inc. All rights reserved.

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