Final answer:
The most critical step is to administer oxygen and request a paramedic unit to give epinephrine, followed by immediate transport to the hospital for a 19-year-old female who is allergic to fire ants and was stung multiple times without having her own epinephrine auto-injector.
Step-by-step explanation:
Given the patient is allergic to fire ants and has been stung multiple times while not carrying epinephrine, an epinephrine injection is crucial to counteract potential anaphylactic reactions. Even though the patient is currently conscious with normal vital signs, allergic reactions can worsen rapidly. The most appropriate immediate actions would be to administer oxygen to support breathing and request a paramedic unit to administer epinephrine, as well as transporting her to the hospital for further care. Positioning her legs above heart level would not address the systemic allergic reaction, and visiting a physician is not immediate enough for a potentially life-threatening reaction. Preparing for potential respiratory distress and plummeting blood pressure, which are hallmarks of anaphylactic shock, is essential and epinephrine is the first line of treatment for such emergencies.