Post-nasal drip (PND) occurs when excessive mucus is produced by the sinuses. The excess mucus accumulates in the throat or back of the nose.Post-nasal drip can be caused by excessive or thick secretions, or impairment in the normal clearance of mucus from the nose and throat.
Various causes for chronic post nasal drip are allergies,viral infections,deviated nasal septum,chronic sinusitis,adenoid enlargement and diseases like sarcoidosis and GERD.
Pls discuss these options with an ENT specialist and get yourself thoroughly examined esp. for sinusitis. Transillumination test and X-Ray or CT sinuses can help in diagnosing it.
Hope it helps.Take care and regards.