Asthma is a common lung disease that causes repeated bouts of wheezing, shortness of breath, chest tightness, and coughing, especially at night or in the early morning. A person with asthma has difficulty breathing because of inflammation and narrowing of the airways.

What is going on in the body?

In a person with asthma, the airways narrow as a result of irritation and inflammation. During an asthma flare-up or "asthma attack," muscles of the airway tubes, or bronchi, tighten. The reaction in the lungs is out of proportion with the amount of stimulation experienced. The inflammation and tightening in the airways increases, trapping air in the lungs. The overreaction to the trigger causes excess mucus to form in the lungs. The person cannot take in a full breath and feels short of breath.

Sometimes the reaction to the trigger causes swelling throughout the entire bronchial tube. The opening in the center of the tube then becomes smaller, and breathing becomes more difficult. When the muscles relax, the bronchial tubes open wider. Asthma symptoms then resolve, and breathing becomes easier.

What are the causes and risks of the disease?

Asthma is caused by an immune system response. The immune system overreacts to triggers and causes the airways to become inflamed and tight. Often there are provoking factors, or triggers, that cause asthma symptoms. Triggers differ from person to person. Asthma triggers include: