Asthma is a disease of lungs in which the airways become blocked or narrowed causing difficulty in breathing. In asthma, the airways also swell up and produce extra mucus. It usually triggers coughing, wheezing or whistling and shortness of breath. The coughing usually occurs at night or early in the morning. The excessive amount of mucus in the passage further narrows the airways because it is sticky and thick. For some people it can be a minor nuisance, whereas for others it can be a major problem that can hinder their daily activities and usually leads to a life threatening asthma attack. Asthma is such a disease that it cannot be cured or treated but its symptoms can be controlled. Asthma can be allergic and non-allergic. Asthma may be due to genetic factor. There are substances that cause allergies (allergens) Iike irritants in the air including smoke from cigarettes, wood-fires, strong fumes, sprays, perfumes or scented soaps, etc., respiratory infections such as cold, flu, sore throat and sinus infections, exercising in cold air (exercise-induced asthma) and some medications such as beta blockers, asprin, non-steroid anti inflammatory drugs, etc.