IL4 and asthma: A shorter and latter intervention might modulate the upstream participants in the pathogenesis of allergic asthma, as evidenced by the increase in splenic Treg cells, an increase in Th1/Th2 ratio, a decrease in asthma-related BALF IL-13 level and the significant decrease in IL-4 and IL-33 levels in the BAL fluid of the 8-day PHF-treated mice; while a longer and earlier PHF-intervention relieve the inflammatory symptoms, including the reduction in airway remodeling and the marked decrease in leucocyte infiltration in the lung of the 14-day PHF-treated mice.