Asthma is a chronic lung disease that affects an estimated 20 million people in the United States. Of these, about 6 million are children under the age of 18 (1.2 million under the age of five). Asthma is also the leading cause of school absenteeism nationwide, leading to 12.8 million school days lost annually. Asthma causes breathing problems. These breathing problems are called episodes (or attacks). In an asthma episode, the airways in the lungs (bronchioles) become narrowed when they react to something in the environment (triggers), causing the lungs to get less air than normal. Symptoms of an asthma episode can include:

• difficulty breathing (shortness of breath)
• a tight feeling in the chest
• coughing
• wheezing