Asthma is an inflammatory condition of the airway, characterized by hyper-responsiveness of the airway to certain trigger factors. These trigger factors can be anything from dust, pollen, cold air, tobacco smoke to physical activity like exercising. Asthma is also marked by an excessive mucous production by cells of the airway. Swelling, increased bronchial responsiveness and excess mucous production, leads to narrowing of the airways, causing episodes of breathing discomfort. https://bit.ly/2LKaakK