Postnasal discharge is a mucus kind of fluid that comes out of the nose. This discharge is observed only when there is excessive production of the mucus by the sinuses in the nasal cavities. This excessive fluid then gets accumulated around the throat and sometimes in the rear region of the nose. In usual days, the quantity of mucus produced by the nose and throat gland is 1-2 quarts per day. This fluid predominantly clears the inhaled irritants like dust, smoke, and dirt to avoid infections. However, when this liquid is produced in excess it drips from the back of the nose. This fluid is then termed as post-nasal drip or sometimes post-nasal drainage.
 
This drainage is accompanied by a series of uncomfortable symptoms. In majority of cases, people tend to consistently swallow this fluid in order to prevent it from drooping out in front of crowd. Secondly, people are most seen spitting this liquid in order to keep the nasal passages clean. It often leads to itching in the outer layer of the throat which leads to cough. In severe cases, people find difficulties in breathing due to immense congestion in the sinus and nasal passages. Few people end up vomiting to exit excess accumulation of mucus inside the stomach.