Asthma is a chronic disease that affects your airways. Your airways are tubes that carry air in and out of your lungs. If you have asthma, the inside walls of your airways become sore and swollen.

In the United States, about 20 million people have asthma. Nearly 9 million of them are children. Children have smaller airways than adults, which makes asthma especially serious for them. Children with asthma may experience wheezing, coughing, chest tightness, and trouble breathing, especially early in the morning or at night.

Many things can cause asthma, including

• Allergens - mold, pollen, animals
• Irritants - cigarette smoke, air pollution
• Weather - cold air, changes in weather
• Exercise
• Infections - flu, common cold

When asthma symptoms become worse than usual, it is called an asthma attack. Asthma is treated with two kinds of medicines: quick-relief medicines to stop asthma symptoms and long-term control medicines to prevent symptoms.