Final answer:
The child with severe anaphylaxis must be treated with epinephrine, the first-line treatment for this life-threatening allergic reaction. Antihistamines and corticosteroids are secondary treatments.
Step-by-step explanation:
The child who presents with severe respiratory distress and signs of anaphylaxis must be treated promptly with epinephrine. This is the first line of treatment for anaphylaxis, which is a life-threatening reaction that can include symptoms such as respiratory distress, plummeting blood pressure, and potential suffocation due to swelling of the throat and tongue. Epinephrine works by constraining blood vessels to increase blood pressure, relaxing smooth muscles in the lungs to improve breathing, and reducing swelling around the airways. In contrast, antibiotics are not effective against anaphylaxis, as most allergens are nonpathogenic. While antihistamines and corticosteroids are also used, they are typically administered after the immediate threat of anaphylaxis has been countered with epinephrine.