Furthermore, significant elevations in IL‐13 gene expression in the HDM + PM/HDM group may explain the enhanced allergic response as IL‐13 plays a pivotal role as a central mediator of allergic inflammation by enhancing IgE production, mucus secretion, eosinophil recruitment, macrophage and dendritic cell activation, as well as airway hyperresponsiveness (Ingram and Kraft 2012). Here, IL13 is linked to airway hyperresponsiveness.