Postnasal drip syndrome: This is the most common cause of upper airway cough syndrome, often resulting from allergic rhinitis, non-allergic rhinitis, or sinusitis, leading to chronic cough due to the irritation of the upper airway by the dripping of secretions from the nose.

Allergic rhinitis: This condition can cause chronic cough through postnasal drip and is a common condition that affects a significant portion of the population.
Non-allergic rhinitis: Similar to allergic rhinitis, non-allergic rhinitis can cause symptoms of postnasal drip leading to cough, without the presence of an allergic response.
Sinusitis: Both acute and chronic sinusitis can lead to upper airway cough syndrome through postnasal drip and direct irritation of the sinuses.

Angiotensin-converting enzyme (ACE) inhibitor-induced cough: Although not as common as other causes, ACE inhibitors can cause a dry, persistent cough in some patients, which is a well-known side effect of these medications.
Gastroesophageal reflux disease (GERD): While more commonly associated with lower respiratory symptoms, GERD can also cause upper airway symptoms, including cough, due to the reflux of stomach contents into the esophagus and potentially into the upper airway.

Foreign body aspiration: Although rare in adults, foreign body aspiration can occur and cause persistent cough among other symptoms, depending on the location and nature of the foreign body.
Laryngopharyngeal reflux: A variant of GERD, laryngopharyngeal reflux involves the reflux of stomach contents into the laryngopharynx, potentially causing cough and other upper airway symptoms.
Vasomotor rhinitis: A less common form of non-allergic rhinitis, vasomotor rhinitis can cause symptoms similar to allergic rhinitis, including postnasal drip and cough, in response to various non-allergic stimuli.