6. Postnasal drip
The purpose of the mucus in our nose and throat is to protect our airways from irritants, objects, and other substances that could get inside them through our nostrils and our mouth. It also cleans the airways from infectious agents such as viruses and bacteria.
We normally produce a small quantity of mucus that covers our airways as a protective layer, and it is thick enough to stay in place and accomplish its purpose. However, for different reasons, sometimes this mucus is more liquid than it should be, so it isn’t consistent enough to stay in place, and slowly drips backward towards our throat due to the effect of the gravity.
This liquid can tickle our throat and trigger our coughing reflex. Since it is a process that happens inside our airways because of its own secretions, the coughing caused by postnasal drip isn’t triggered by any Ambiental factor or infection, and thus is more difficult to identify.