What is Asthma?

Normal Airway

Airway with Inflammation

Airway with Inflammation, Bronchospasm and Mucus Production

Asthma is a chronic respiratory disease—sometimes worrisome and inconvenient—but a manageable condition. With proper understanding, good medical care, and monitoring, you can keep asthma under control.

If you have asthma you are not alone. In the United States, asthma affects 14 to 15 million people. Today, 10 million adults have asthma. Asthma, also known as reactive airway disease, is defined as a chronic lung condition with:

• Inflammation (swelling) of the airways
• Increased sensitivity of the airways to a variety of things that make asthma worse
• Obstruction of airflow

Typical Changes in the Airway Include:

Inflammation

Recent research has shown that inflammation of the lining of the airways is the most common feature of asthma. When they are stimulated, certain cells lining the airways release chemical substances (mediators) that lead to inflammation. This causes the airway lining to swell and narrow. The inflammation may last for weeks following an episode. Most people with asthma have some degree of inflammation all of the time. Some long-term control medications can help prevent and reduce inflammation.

Read more about inflammation in asthma.

Increased Sensitivity

Another characteristic of asthma is increased sensitivity of the airways. When inflammation occurs in the airways, the airways become more sensitive. When the airways are more sensitive, you are more likely to have asthma symptoms when exposed to things that make asthma worse. When there is less inflammation, the airways are less sensitive and you are less likely to have asthma symptoms when exposed to things that make asthma worse.

Airway Obstruction

In addition to inflammation, further airway obstruction sometimes occurs with asthma. Obstruction is caused by tightening of muscles that surround the airways. This is also called bronchospasm. Bronchospasm causes further narrowing of the inflamed airways. Inhaled quick-relief medications are generally very effective in reversing the bronchospasm.

In some people with asthma, the mucus glands in the airways produce excessive, thick mucus, further obstructing the airways.

This information has been approved by David Tinkelman, M.D. (February 2006).