Why do we cough?
Short answer
Coughing is an automatic response that helps protect the airways—the passages that carry air from the throat to the lungs.
How it works
When something irritates one of these passages, the body takes in air. The opening to the windpipe briefly closes. The chest and belly muscles tighten, squeezing the air inside. When the opening reopens, air rushes out and can carry mucus (a fluid in the airways) or the irritant with it.
Colds, allergies, and irritants such as smoke can all trigger coughs. If a cough lasts more than three weeks or breathing is difficult, seek medical advice promptly.