In some clinics, when we are going to perform an image exam, we usually answer a questionnaire. One of the questions is: do you have a shrimp allergy? When the answer is yes, they recommend doing the test without using a contrast medium or looking for an allergist. After all… who is allergic to shrimp cannot have an image exam using the iodine contrast medium? Allergy to shrimp or to other seafood does not contraindicate the use of iodine contrast. Contrasts are substances administered during a radiological examination in order to facilitate the observation of certain organs or anatomical structures. Reactions to iodinated contrast media can be: – Hypersensitivity reactions, which may be allergic or non-allergic. – Toxic reactions. Hypersensitivity reactions can be immediate (occur within the first hour of administration) and non-immediate (occur later after administration). The frequency of reactions is 0.5 to 3% in people who have received non-ionic iodinated contrast. Iodinated contrasts can be ionic (high osmolarity) or non-ionic (low osmolarity). In computerized tomography, iodinated contrast is used; while in magnetic resonance, gadolinium is used. Allergic manifestations can be mild, moderate or severe. They come in many forms: itching and reddish plaques on the skin, swelling of the eyelids and lips, stuffy nose, sneezing, shortness of breath, tightness in the throat, chest pain, racing heat, drop in blood pressure and even loss of consciousness. People most at risk are those who have had a previous reaction. Each patient must be evaluated individually and, in selected cases, premedication may be used before the imaging exam is performed. Don’t keep in doubt, look for an allergist!
References:
1) Torres MJ, Trautmann A, Böhm I, Scherer K, Barbaud A, Bavbek S, Bonadonna P, Cernadas JR, Chiriac AM, Gaeta F, Gimenez-Arnau AM, Kang HR, Moreno E, Brockow K. Practice parameters for diagnosing and managing iodinated contrast media hypersensitivity. Allergy. 2021 May;76(5):1325-1339. doi: 10.1111/all.14656. PMID: 33170954
2) Posicionamento da Associação Brasileira de Alergia e Imunologia sobre contrastes em radiologia – 201
