Radioiodine treatment of differentiated thyroid cancer despite history of ‘iodine allergy’

Radioiodine ((131)I) is a critical component in the treatment of differentiated thyroid cancer. We recently saw a patient with thyroid cancer who was hesitant to take (131)I treatment because he had previously encountered an allergic reaction to administration of iodine-containing radiocontrast agent for computed tomography (CT) scanning. We were able to administer (131)I treatment after discussion that his anaphylactic reaction was not due to iodine and that radioiodine ((131)I) treatment is unlikely to cause a reaction in the patient. LEARNING POINTS: An allergy to iodine itself does not exist. When patients claim that they have an ‘iodine allergy’, ask them what substances they are allergic to and what kind of reaction occurred during use of such substances. Radioactive iodine is not a contraindication for patients who claim an ‘allergy to iodine’.