Causes & Risks
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 swell. This reduces the amount of air that can pass by, and can lead to wheezing sounds.
Most people with asthma have wheezing attacks separated by symptom-free periods. Some patients have long-term shortness of breath with episodes of increased shortness of breath. In others, a cough may be the main symptom. Asthma attacks can last minutes to days and can become dangerous if the airflow becomes severely restricted.
In sensitive individuals, asthma symptoms can be triggered by breathing in allergy-causing substances (called allergens or triggers).
Common asthma triggers include:
- Animals (pet hair or dander)
- Changes in weather (most often cold weather)
- Chemicals in the air or in food
- 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 an individual or family history of allergies, such as hay fever (allergic rhinitis) or eczema. Others have no history of allergies.