Does post nasal drip cause constant throat clearing?

Yes. When body produces excessive mucus, thicker than normal does it become problem when the mucus runs down the back of the nose to the throat, it's called postnasal drip.Colds, flu allergies (called allergic postnasal drip), sinus infection or sinusitis are most common causes. Postnasal drip creates an annoying feeling that makes you want to constantly clear your throat. Antihistamines help.