Asthma is a chronic disease that causes the air passageways in the lungs to become blocked or narrowed, making it more difficult to move air into and out of the lungs. Inflammation causes the airway tubes to swell, limiting the available space for air to move through. If you have asthma, you have it all the time but your symptoms may vary from none at all to mild breathing impairment to extreme difficulty breathing, as happens during a severe "asthma attack." When symptoms occur, treatment may be required to restore normal breathing.
An estimated 20 million adults and children in America have asthma. It is the most common chronic childhood disease and, according to the Centers for Disease Control and Prevention (CDC), nearly one in every five pediatric emergency room visits is related to asthma.