A 27-year-old woman develops progressive difficulty breathing after a long day of chores in a dusty house. These chores included brushing the family dog, vacuuming, dusting, and sweeping. She occasionally gets these episodes once or twice a year and has her medication on hand. Her symptoms are relieved by inhaling a β2-adrenergic receptor agonist. What chemical mediators are responsible for this patient’s breathing difficulties &why?