Patients with shellfish allergy may have a concurrent risk for an allergic reaction to what contrast agent used in diagnostic imaging?

• A. Iodinated contrast dye
• B. Gadolinium-based contrast
• C. Barium sulfate
• D. Air contrast

Answer: (A)

The key idea is that iodine-containing contrast media carry the risk of allergic-type reactions in sensitive individuals, and shellfish allergy is commonly taught as a context where iodinated contrast dye is a concern. In diagnostic imaging, iodinated contrast is used for CT and many angiographic studies, so awareness of potential hypersensitivity to this agent is important. If a reaction occurs, it can range from mild symptoms like hives to more severe airway or circulatory compromise, requiring prompt reversal and supportive treatment. The other contrast options have different use contexts and risk profiles not specifically linked to shellfish allergy: gadolinium-based contrast is used in MRI and can cause rare reactions with additional kidney-related risks, barium sulfate is used for GI imaging and is not iodine-containing, and air contrast is a technique rather than a chemical agent.