Final answer:
The nurse should prioritize obtaining detailed information about the client's previous allergic reaction to a certain medication, as this guides the subsequent actions including potential changes to treatment and emergency preparedness.
Step-by-step explanation:
When a client mentions an allergy to a type of medication, the nurse's priority action should be to obtain detailed information about the client's previous reaction to the specific medication. This is crucial because it allows for understanding the nature and severity of the allergic reaction, which could range from mild symptoms treatable with antihistamines to potentially life-threatening reactions like anaphylaxis. The nurse can then share this information with the healthcare provider for an appropriate clinical decision, which might include altering medications, notifying the healthcare team, educating the client, or in some cases, immediate discontinuation of medication. It is essential to be equipped to treat severe allergic reactions, which may require emergency administration of epinephrine and follow-up treatment with antihistamines and corticosteroids.