A single cough is caused by a very quick chain of events...
The brain reacts to special receptor nerves in the airways that have indicated there might be a problem – the delicate hairs (known as cilia) that normally transport mucus out of the airways have become blocked by sticky phlegm, or irritated in some way.
To try and expel the irritant a quick expulsion of air is propelled from deep within the lungs. This happens at great speed - some report up to 50 miles per hour.
Duration of a Cough
How long a cough lasts is a very different matter and depends largely on the cause.
There's no quick-fire way of curing a cough that's caused by a viral infection. It will usually clear up after your immune system has fought off the virus which can mean anything from two to three days to a couple of weeks.
You may find that using an appropriate cough medicine or hot drink can help by either thinning and loosening irritating mucus or soothing irritated areas.
It is important to stress that if a cough goes on for longer than two weeks after a virus, or gets progressively worse, you should talk to your doctor.
When to visit your GP
While coughs are generally a natural immune response by the body it is worth stressing here that any cough:
that persists for more than two weeks
or that gets progressively worse
or that contains blood or large amounts of darker green or yellow phlegm should be seen by a GP