Clinically, e‐cigs have been shown to directly impact lower airway epithelial cells in a similar manner as conventional cigarettes resulting in functional changes such as increased airway resistance and airway obstruction, symptomatic immune suppression, mucin production, irritation and inflammation, and lung disease exacerbation.16, 21, 22, 162, 163. This evidence concerns the gene MUC5AC and Airway obstruction.