Final answer:
The priority nursing intervention for a client experiencing anaphylactic reaction is to administer epinephrine.
Step-by-step explanation:
The priority nursing intervention for a client experiencing an anaphylactic reaction is to administer epinephrine. Epinephrine helps to control the immune reaction by constricting blood vessels to increase blood pressure, relaxing smooth muscles in the lungs to improve breathing, modulating heart rate, and reducing swelling that may block the airways. By administering epinephrine, the nurse can counteract the life-threatening symptoms of anaphylaxis and provide immediate relief to the client.