Post-nasal drip Post-nasal drip Post-nasal drip (PND, also termed upper airway cough syndrome, UACS, or post nasal drip syndrome, PNDS) occurs when excessive mucus is produced by the nasal mucosa. The excess mucus accumulates in the back of the nose and eventually the throat once it drips down the back of the throat. It is caused by rhinitis, sinusitis, gastroesophageal reflux disease (GERD), or by a disorder of swallowing (such as an esophageal motility disorder). But also further sources such as an allergy, cold or flu and as a result of medications. However, researchers argue that the flow of mucus down the
Nasal infix would be expected. For example, the PIE root "to win" would yield a nasal-infixed present stem . These presents are called "nasal infix presents" or simply "nasal presents" and are typically active transitive verbs, often with durative aspect. Since the linguistic ancestor of PIE is not known, there can only be speculations about the origins of the nasal infix. It has been suggested that it arose from a suffix (also related to and ) which underwent metathesis. Besides the nasal infix, PIE employs a number of affixes to mark the present: , , , , , and others. All in