What is Asthma?

Woman using asthma inhaler
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Medical Specialties:

Allergy/immunology, Emergency medicine, Family medicine, Internal medicine, Pulmonology

Clinical Definition:

Asthma is a chronic inflammatory disease of the lungs characterized by increased airway reactivity in response to certain stimuli. During an asthma exacerbation, constriction of the smooth muscle of the bronchi, increased mucus production and mucosal edema, or swelling, occur, which creates the clinical presentation of respiratory distress.

In Our Own Words:

Asthma is a chronic medical condition affecting the lungs. People who have asthma have airways that are sensitive to certain things that generally don’t bother other people. Various stimuli, known as triggers, can cause an asthma attack. Common triggers include fur, dander, dust, smoke, exercise and cold weather.

During an asthma attack, the airways tighten, and inflammation or swelling occurs. The tightening and swelling makes the airways narrow. There is also an increase in mucus production. This combination of factors makes getting air in and out of the lungs difficult.

More Information About Asthma

People with asthma exhibit a special type of inflammation that increases response to triggers to which people without asthma are less susceptible. These triggers result in (mostly) reversible narrowing of the airways, decreased airflow and wheezing and trouble breathing (dyspnea).

Asthma affects about 300 million people throughout the world. After decades of increase, the number of people with asthma has stabilized most recently, and about 15 percent of children and 10 to 12 percent of adults have the disease.

Most people who live in the Western world develop asthma due to atopy, or allergies.

These people are usually allergic to dust mites, pollen and animal dander or fur.

Although asthma can present at any age, it usually is first noticed in children at age 3. About twice as many boys than girls have asthma. By adulthood, an equal number of men and women have the disease.

In many people with asthma as children, this disease abates by adulthood. However, asthma can return. Furthermore, people with mild asthma rarely develop severe asthma, and those with severe asthma have severe asthma from the beginning and don't later experience mild asthma.

Both genetic and environmental factors predispose a person to the development of asthma.

In addition to the triggers mentioned above, other asthma triggers include infection (think rhinovirus or the common cold), pollution, stress, gastroesophageal reflux disease (GERD), and hormone changes experienced before menstruation.

Here are some risk factors that may contribute to the development of asthma:

  • obesity
  • low birth weight
  • prematurity
  • lower maternal age
  • inactivity

Here are some ways that asthma is treated:

  • avoidance of triggers;
  • bronchodilators like B2 agonists (think albuterol inhaler), which relax smooth muscle in airways and act quickly;
  • inhaled corticosteroids, which help reduce inflammation and are very effective;
  • systemic corticosteroids, which are taken by mouth.

A portable nebulizer or breathing machine can be used to administer asthma medication at home.


Cleveland Clinic. “Asthma Overview.” Accessed September 2013.

Cleveland Clinic. “Asthma Symptoms.” Accessed September 2013.

Asthma and Allergy Foundation of America. “Asthma Basics.” Accessed September 2013.

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