A 7-Year-Old Boy Is Brought to the Emergency Department by His

A 7-year-old boy is brought to the emergency department by his mother because of difficulty breathing for 20 minutes. He was having lunch with his mother when she noticed a rash and swelling of his tongue and lips. His temperature is 37°C (98.6°F) , pulse is 169/min, respirations are 28/min, and blood pressure is 90/50 mmHg. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination shows generalized hives, swelling of his tongue and lips, and labored breathing with intercostal retractions. Which of the following is most responsible for this patient's current condition?

A) Gram-negative bacterial endotoxin
B) Gram-positive bacterial exotoxin
C) Kallikrein-generated bradykinin
D) Mast cell-derived histamine
E) Vasoactive intestinal peptide