Asthma is a chronic disease of the air passages in the lungs. Actual causes of asthma are not known. However, asthma experts believe that a combination of genetic and environmental factors (such as family history, childhood viral infections, and early allergen exposure), can cause asthma or at least make a person sensitive to asthma triggers. However, no one really knows why some people are affected by asthma and others are not. Allergies often are associated with asthma. But not all people with allergies suffer from asthma. While asthma causes are not known, doctors have identified two main causes of asthma symptoms:


If you have asthma, the lining – or inside walls – of the airways are inflamed (or swollen). This inflammation makes the air passages particularly sensitive to irritants and asthma triggers. The swelling narrows the air passages, making it difficult for air (and oxygen) to pass through the airways and making it hard to breathe in and out.

Airway Constriction

To further complicate things, when the airways come into contact with certain asthma triggers, the muscles around the airways tighten. This causes the air passages to become even narrower and gives you a tight feeling in the chest, like a rope is being tightened around it. Mucus can get lodged in the narrowed airways, causing more breathing difficulties.

Asthma Triggers

The triggers that cause the inflammation and airway constriction can vary in different people. What is known is that when the airway comes in contact with one of many asthma triggers, it becomes inflamed, constricts, and fills with mucus. The lining of the airway swells, causing the airway to narrow.

Asthma triggers include:

  • Pollen
  • Dust mites, cockroaches
  • Mold
  • Pet hair or dander
  • Changes in weather (especially cold air)
  • Respiratory infections (such as the common cold)
  • Tobacco smoke
  • Stress and strong emotions
  • Exercise and physical activity
  • Allergic reaction to food or sulfites (food preservatives)
  • Heartburn/acid reflux
  • Certain medications (aspirin, beta blockers)