Thank you for your inquiry.
The vast majority of the literature exposing the myth that iodine allergy is related to shellfish, and that allergy to shellfish is to the iodine component, deals with the relationship between shellfish allergy and the iodine contained in radiocontrast material. This is probably because as opposed to contact dermatitis reactions to iodine (such as in Betadine), reactions to radiocontrast are potentially fatal. However, this work (three references are copied for you below which will give you all of the information you need in their bibliography) has clearly found that shellfish allergy has absolutely nothing to do with iodine, and that the allergen in shellfish is a muscle component, not iodine. Thus this work clearly indicates that there is no increased risk for contact dermatitis to Betadine or any other iodine-containing antiseptic. Thus, you may be reassured that Betadine or any other iodine-containing antiseptic can be used without any increased risk in patients who have shellfish allergy.
Thank you again for your inquiry and we hope this response is helpful to you.
J Emerg Med. 2010 Nov;39(5):701-7. doi: 10.1016/j.jemermed.2009.10.014. Epub 2010 Jan 4.
The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed.
Schabelman E, Witting M.
Department of Emergency Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
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.
Seafood and Iodine: An Analysis of a Medical Myth
Allergy and Asthma Proceedings, Volume 26, Number 6, November-December 2005 , pp. 468-469(2)
Author: Huang, Shih-Wen
There is a prevailing myth that iodine levels in seafood and seafood allergy are connected. Therefore, we designed a study to collect information about this misconception from patients referred to our pediatric allergy clinic because of suspected seafood allergy. We presented five questions to our patients, and the most surprising result was that the majority of them believe that iodine is linked to seafood allergy. As a result, many felt uneasy about the use of iodine radiocontrast media. A survey of iodine content in common foods showed that, although the iodine content of seafood is higher than nonseafood items, daily consumption of the latter is much greater and, therefore, any phobia about iodine in seafood is unfounded. We encourage strong public education about seafood allergy by allergy specialists.
The American Journal of Medicine, Volume 121, Issue 2, February 2008, Pages 158.e1–158.e4
Seafood Allergy and Radiocontrast Media: Are Physicians Propagating a Myth?
Background: Recent surveys have indicated that the misconception that seafood allergy confers a disproportionately increased risk of adverse reactions to radiocontrast media remains pervasive among physicians and patients. One possible explanation for the persistence of this notion is that physicians responsible for radiocontrast administration are inadvertently contributing to its propagation.
Methods: An anonymous survey was sent to 231 faculty radiologist and interventional cardiologists at 6 Midwest academic medical centers. Two questions dealt directly with seafood allergy related to radiocontrast media administration, and 6 questions served as distracters
Results: Sixty-nine percent of responders indicated that they inquire about a history of seafood allergy before radiocontrast media administration. Some 37.2% of responders replied that they would withhold radiocontrast media or recommend premedication on the basis of a history of seafood allergy.
Conclusion: Even among faculty physicians at university medical centers, the notion of seafood allergy as a significant risk factor for adverse radiocontrast media reactions remains pervasive. Even if no action is taken on the basis of the answer, it seems probable that the act of inquiring about seafood allergy before radiocontrast media administration could lead patients and trainees to presume an inherent risk in patients who are seafood allergic, thus propagating the notion. Physician education with respect to seafood allergy and radiocontrast media administration is vital to halting the persistence of this misconception.
Phil Lieberman, M.D.