|Classification and external resources|
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 throat or back of the nose. It is caused by rhinitis, sinusitis, gastroesophageal reflux disease (GERD), or by a disorder of swallowing (such as an esophageal motility disorder). It is frequently caused by an allergy, which may be seasonal or persistent throughout the year.[medical citation needed]
However, other researchers argue that mucus dripping down the back of the throat from the nasal cavity is a normal physiologic process that occurs in healthy individuals. Post-nasal drip syndrome as a concept has been challenged due to a lack of an accepted definition, a lack of any pathologic tissue changes and no available biochemical tests. The phrase has been described as a "pseudo-syndrome" (i.e., not a real medical condition) which serves as a catch-all, waste-basket phrase that is unhelpful.
PND is suggested to be a cause of extra-oral halitosis, especially when a sinus infection is also present. Acid reflux or heartburn is believed to aggravate and in some cases cause post-nasal drip.
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