Asthma is a disease that affects the breathing passages of the lungs (bronchioles). Asthma is caused by chronic (ongoing, long-term) inflammation of these passages. This makes the breathing tubes, or airways, of the person with asthma highly sensitive to various "triggers."
Because asthma causes resistance, or obstruction, to exhaled air, it is called an obstructive lung disease. The medical term for such lung conditions is chronic obstructive pulmonary disease or COPD. COPD is actually a group of diseases that includes not only asthma but also chronic bronchitis and emphysema. Some people with asthma do not have COPD. These are the individuals whose lung function returns to normal when they are not having an attack. Others will have a process of lung airway remodeling from chronic, long-standing inflammation, usually untreated. This results in permanent abnormalities of their lung function with symptoms of obstructive lung disease occurring all the time