What Is Asthma?

Asthma is a chronic disease of the airways that makes breathing difficult. With asthma, there is inflammation of the air passages that results in a temporary narrowing of the airways that carry oxygen to the lungs. This results in asthma symptoms, including coughing, wheezing, shortness of breath, and chest tightness. Some people refer to asthma as “bronchial asthma.”

Even though there are seemingly miraculous treatments for asthma symptoms, asthma is still a serious -- even dangerous -- disease that affects more than 22 million Americans and causes nearly 2 million emergency room visits ever year. With proper asthma treatment, you can live well with this condition. Yet inadequate asthma treatment limits the ability to exercise and be active. Poorly controlled asthma can lead to multiple visits to the emergency room and even hospital admission, which can affect your performance at home and work.

In each of the following sections, there are in-depth articles that link to the topics. Be sure to read each health topic so you have a greater understanding of asthma and how it is diagnosed and treated.

There are three major features of asthma:

1. Airway obstruction. During normal breathing, the bands of muscle that surround the airways are relaxed, and air moves freely. But in people with asthma, allergy-causing substances and environmental triggers make the bands of muscle surrounding the airways tighten, and air cannot move freely. Less air causes a person to feel short of breath, and the air moving through the tightened airways causes a whistling sound known as wheezing.

(Fortunately, this airway narrowing is reversible, a feature that distinguishes asthma from other lung diseases such as bronchitis or emphysema.)

2. Inflammation. People with asthma have red and swollen bronchial tubes. This inflammation is thought to contribute greatly to the long-term damage that asthma can cause to the lungs. And, therefore, treating this inflammation is key to managing asthma in the long run.

3. Airway irritability. The airways of people with asthma are extremely sensitive. The airways tend to overreact and narrow due to even the slightest triggers such as pollen, animal dander, dust or fumes.

Adult-Onset Asthma

Asthma affects 22 million Americans. Asthma may occur at any age, although it's more common in younger individuals (under age 40).

People who have a family history of asthma have an increased risk of developing the disease. Allergies and asthma often occur together. Smoking with asthma, a dangerous combination, is still seen commonly.

However, anyone can develop asthma at any time, and adult-onset asthma happens frequently. If you have symptoms of asthma, talk to your doctor. If you have adult-onset asthma, your doctor will instruct you in using the asthma inhalers and other asthma medications to prevent further breathing problems.

For more information, see WebMD's Adult-Onset Asthma.