Asthma is a disease that affects the medium-sized airways in the lungs. During an attack, the airways narrow and fill up with mucus. These effects can be reversed by medical treatment, using inhalers and oral medication.
Chronic obstructive airways disease is characterised by airflow obstruction due to chronic bronchitis or emphysema. Chronic bronchitis is defined as the presence of a productive cough for at least three months in at least two successive years. Chronic obstructive airways disease mainly affects middle-aged and older people. A preventable condition, it is caused by exposure to cigarette smoke. Medical treatment is generally less successful than that for asthma.