Asthma is a chronic lung disease that inflames and narrows the airways. Asthmas cause recurring periods of wheezing, chest tightness, shortness of breath, and coughing. The coughing often occurs at night or early in the morning. Asthma affects people of all ages but it most often starts during childhood. Asthma can be caused by invasion of the external pathogenic factors, diet, emotional disturbance congenital weakness and chronic illness.