Inflammation of the airways causes the symptoms of asthma (wheezing, breathlessness, chest tightness and coughing) by restricting the airflow to and from the lungs. It does this by causing:
- Swelling of the airways which makes them narrower.
- Tightening of the muscles that surround the airways, making them even narrower. This is also called bronchoconstriction.
- The production of too much mucus, which can plug up or block the airways.
- Longer-term damage to the walls of the airways, which prevents them from opening as widely as a normal airway.
When the airways have been inflamed for a long time, they become extra-sensitive. This means that they react faster and more strongly to various triggers such as allergens, viruses, dust, smoke and stress.