If a patient exhibits signs of an allergic reaction, what should the nurse do first?

The appropriate first action for a nurse when a patient shows signs of an allergic reaction is to stop the offending medication. This step is critical because continuing the administration of the medication may exacerbate the patient's reaction and could lead to more severe complications. By halting the medication, the nurse minimizes further exposure to the allergen, which can be lifesaving, particularly in cases where the patient could progress to anaphylaxis.

Stopping the medication also facilitates further assessment and management of the allergic reaction, allowing healthcare providers to implement interventions such as administering appropriate medications (like antihistamines or epinephrine) if needed. The other options, while important in the overall management of the allergic reaction, follow the priority of removing the causative agent from the patient’s system. Documenting symptoms and providing reassurance are crucial for patient care, but they do not address the immediate threat that the medication presents to the patient.