Asthma is a disease that affects the breathing passages of the lung (bronchioles). Asthma is caused by chronic (ongoing, long-term) inflammation of these passages. This makes the breathing passages, or airways, of the person with asthma highly sensitive to various "triggers."
When the inflammation is "triggered" by any number of external and internal factors, the passages swell and fill with mucus. Muscles within the breathing passages contract (bronchospasm), causing even further narrowing of the airways. This narrowing makes it difficult for air to be breathed out (exhaled) from the lungs. This resistance to exhaling leads to the typical symptoms of an asthma attack.
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. Like any other chronic disease, asthma is a condition you live with every day of your life. You can have an attack any time you are exposed to one of your triggers. Unlike other chronic obstructive lung diseases, asthma is reversible.
Asthma cannot be cured, but it can be controlled you have a better chance of controlling your asthma if it is diagnosed early and treatment is begun right away. With proper treatment, people with asthma can have fewer and less severe attacks. Without treatment, they will have more frequent and more severe asthma attacks and can even die.