A nurse is caring for Joseph, a patient who developed mucosal swelling, urticaria, and swollen face and eyes after starting amoxicillin. His respiratory rate is 24/min, heart rate is 110/min, and lungs are clear but breathing is labored. What nursing action should have the highest priority?

A. Obtain a complete allergy history: This is important for the future, but in an active anaphylactic crisis, it is a low priority compared to life-saving intervention. B. Apply a cool compress: This is a comfort measure for mild localized reactions; it does nothing to stop the systemic life-threatening airway obstruction. C. Administer epinephrine immediately: The patient is showing signs of anaphylaxis (labored breathing, swelling, tachycardia). Epinephrine is the first-line treatment to reverse bronchospasm and cardiovascular collapse. D. Administer oral antihistamines: Oral medications are absorbed too slowly for an emergency, and antihistamines do not treat the life-threatening airway constriction or hypotension associated with anaphylaxis.