Is there an association between iodine, shellfish, and contrast agents?
Date First Published:
July 1, 2019
Last Updated:
August 30, 2019
Report by:
Benjamin Long MD, Todd Chassee MD, EM Senior Resident, EM Faculty (Spectrum Health/Michigan State University Emergency Medicine Residency Program)
Search checked by:
Jeffrey S. Jones, MD, Spectrum Health/Michigan State University Emergency Medicine Residency Program
Three-Part Question:
What is the risk of an [adverse reaction] in [patients with iodine or shellfish allergies] who [receive radiocontrast media]?
Clinical Scenario:
An emergency department patient needs a computed tomography angiogram to rule out a pulmonary embolism. The patient has a shellfish allergy noted on the medical record and you wonder if it is safe for the patient to receive intravenous radiocontrast.
Search Strategy:
Medline 1966-07/19 using PubMed, Cochrane Library (2019), Google Scholar, and Embase
Search Details:
[(contrast media/adverse effects OR contrast media reactions) AND (exp shellfish/adverse effects OR exp iodine/adverse effects OR exp food Hypersensitivity)]. Limit to English language.
Outcome:
199 studies were identified; one systematic review article specifically addressed the clinical question.
Relevant Paper(s):
| Study Title | Patient Group | Study type (level of evidence) | Outcomes | Key results | Study Weaknesses |
|---|---|---|---|---|---|
| The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed Schabelman E, Witting M Nov-10 United States | 6 articles were included | Systematic review | Risk of contrast reaction in all cases compared to persons with known allergies to seafood, food allergens, asthma, and prior contrast reactions | Allergies to seafood does not increase the risk of reaction to contrast any more than a history of other allergies or asthma | Several studies are based on high osmolar contrast medium which has been largely replaced by low osmolar contrast medium |
Author Commentary:
Millions of imaging studies using radiocontrast media are conducted each year, providing vital information for patient care. Adverse reactions to contrast media are rare and are mostly dependent on the osmolar weight of the contrast media. The risk of reaction increases with a history of asthma or food allergy including eggs, milk, chocolate, fruit and seafood. Seafood does not predispose to a greater risk with regards to severity of reaction or incidence of reaction compared to any other allergy. Iodine is found throughout our bodies in thyroid hormones and amino acids and cannot be an allergen.
Bottom Line:
There is no evidence that allergy to shellfish or iodine alters the risk of reaction to intravenous contrast more than any other allergy.
References:
- Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed