A cough is one of the body’s built-in airway-clearing reflexes.
When sensitive nerves detect irritation, mucus, particles, or other problems in the throat or airways, they can trigger a coordinated burst of air.
That burst is meant to move material out.
A cough begins with a warning signal
The lining of your respiratory tract contains sensory nerves.
Smoke, dust, mucus, food, infection, inflammation, and other irritants can activate them.
Those nerves send information toward the brain.
The brain then coordinates muscles in the chest, abdomen, throat, and airway.
What physically happens during a cough?
A typical cough includes several steps.
You take in air.
Part of the throat closes briefly.
Muscles build pressure inside the chest.
Then the airway opens suddenly and air rushes outward at high speed.
That air can carry mucus or irritating material with it.
Why do colds make you cough?
Respiratory viruses can inflame the tissues lining the airways.
Inflamed tissue becomes more sensitive.
Mucus production may increase too.
Even after the main infection begins improving, irritated airways can remain sensitive for a while, which helps explain why a cough can linger.
Does every cough mean something is stuck?
No.
Asthma, allergies, reflux, smoke exposure, dry air, medications, and many other conditions can trigger coughing.
Sometimes the airway is reacting to irritation rather than trying to remove a physical object.
Why is coughing worse at night for some people?
Lying down can change drainage, reflux, and airway irritation.
Dry indoor air can contribute too.
Different causes produce different patterns, so there is no one night-cough explanation that fits everybody.
Is coughing always helpful?
The reflex itself has a protective purpose, but persistent coughing can become exhausting and irritating.
A cough associated with trouble breathing, coughing up blood, severe chest pain, high fever, or other serious symptoms deserves medical attention.
The ordinary cough, though, is not your body malfunctioning.
It is your airway trying to clean house.
Useful system.
Terrible soundtrack.
The same body systems connect with Why do we sneeze?, another everyday effect with its own underlying mechanism.
And that’s the short explanation.
Related explanations: Why do we sneeze?, Why does your nose get stuffy?, and Why does snot turn green?