It has been extensively documented by using various experimental models of asthma that HDM exposure triggers airway inflammation associated with increased infiltration into the lungs of various immune cells, including eosinophils, lymphocytes, neutrophils and macrophages, and that this is accompanied by an increase in AHR, goblet cell hyperplasia, smooth muscle thickening and airway remodelling (30–32). Here, AHR is linked to asthma.