Postnasal drip is a common condition that occurs when excess mucus drains from the sinuses down the back of the throat. It can be caused by allergies, colds, sinus infections, or even changes in the weather. While it’s often associated with a sore throat, coughing, or a constant need to clear your throat, many people also experience nausea. But how exactly does postnasal drip cause nausea and what can you do to find relief ...