Yes, there is a difference between potassium iodide for use in nuclear incidents and injected iodine for medical exams. Potassium iodide is used to protect the thyroid gland from radioactive iodine, while injected iodine is used as a contrast agent in medical imaging exams. Allergic reactions to iodine are rare, and typically result from other molecules attached to the iodine rather than the iodine itself. It is important to be aware of any potential allergies to ingredients in medications or contrast agents, but potassium iodide itself does not typically cause allergic reactions.