Definition of Asthma:

Asthma is a disorder that causes the airways of the lungs to swell and narrow, leading to wheezing, shortness of breath, chest tightness, and coughing.

See also:

• Pediatric asthma
• Work-related asthma

Causes, incidence, and risk factors:

Asthma is caused by inflammation in the airways. When an asthma attack occurs, the muscles surrounding the airways become tight and the lining of the air passages swells. This reduces the amount of air that can pass by.

In sensitive people, asthma symptoms can be triggered by breathing in allergy-causing substances (called allergens or triggers).

Common asthma triggers include:

• Animals (pet hair or dander)
• Dust
• Changes in weather (most often cold weather)
• Chemicals in the air or in food
• Exercise
• Mold
• Pollen
• Respiratory infections, such as the common cold
• Strong emotions (stress)
• Tobacco smoke

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) provoke asthma in some patients.

Many people with asthma have a personal or family history of allergies, such as hay fever (allergic rhinitis) or eczema. Others have no history of allergies.