Postnasal drip The sinuses, throat, and nose all produce mucus that a person usually swallows unconsciously. When mucus starts to build up or trickle down the back of the throat, this is known as postnasal drip. Causes of postnasal drip include infections, allergies, and acid reflux.
If your mucus is dry and you are having trouble coughing it up, you can do things like take a steamy shower or use a humidifier to wet and loosen the mucus. When you do cough up phlegm (another word for mucus) from your chest, Dr. Boucher says it really doesn't matter if you spit it out or swallow it.