From the Guidelines
You can experience reactions to iodine-containing substances, but true iodine allergies are rare and most reactions are not to the iodine itself. When considering the risk of allergic reactions to iodine, it's essential to distinguish between reactions to iodine and reactions to substances that contain iodine, such as iodinated contrast media used in medical imaging or seafood. According to the most recent and highest quality study 1, reactions to iodinated contrast media do not relate to iodine, and the term “iodine allergy” should not be used in the context of these reactions. The study also highlights that drug-induced anaphylaxis, including reactions to contrast media, can be severe and life-threatening, and are associated with significant mortality rates. Key points to consider include:
- Reactions to iodine-containing substances can occur, but are often due to other components rather than the iodine itself 1.
- People with seafood allergies do not necessarily have reactions to iodine, as these reactions are typically caused by proteins in the seafood rather than iodine content 2.
- If you suspect a reaction to an iodine-containing substance, it's crucial to inform healthcare providers before procedures involving contrast dyes, as they can take precautions such as using alternative imaging techniques or providing premedication with antihistamines or steroids 2.
- Consultation with an allergist is recommended for proper evaluation and management of suspected reactions to iodine-containing substances.
From the Research
Allergic Reactions to Iodine
- Iodine is a trace element required to produce thyroid hormone, and it does not stimulate an immune response, making it unlikely to cause an allergic reaction 3.
- The term "iodine allergy" is often misused, as it can refer to allergies against different substance classes, such as disinfectants with complexed iodine and contrast media containing covalently bound iodine 4.
- Studies have shown that there is no relationship between iodine and adverse reactions to iodine-containing products, and that the alleged "iodine allergy" is a potentially dangerous concept that can lead to inferior radiologic management and adverse drug reactions 4.
Cross-Reactivity Between Iodine-Containing Compounds
- There is a lack of evidence to support cross-reactivity between iodine-containing compounds in individuals with alleged "iodine allergy" 5.
- Iodine has not been shown to be the allergen responsible for allergic reactions to iodinated contrast media, amiodarone, povidone-iodine, and other iodine-containing compounds 5.
- The use of gadolinium, which has a different chemical structure and no cross-reactivity with iodine-based contrast media, may be a suitable alternative for patients with contraindications to iodine contrast due to allergy or renal failure 6.
Clinical Implications
- The diagnosis "iodine allergy" can lead to uncertainty in clinical management, resulting in unenhanced scans and sometimes unnecessary prophylactic actions 4.
- Clinicians should assess patients for allergies and seek input on the cause of any previous reactions to iodine-containing substances, rather than relying on a diagnosis of "iodine allergy" 3.
- Education efforts are needed to clarify misconceptions about iodine "allergies" and to ensure that patients receive appropriate care, including the use of iodinated contrast media when necessary 7.