Inflammation of the lining of the nose from any cause generally results in swelling and increased thick mucus production. So post-nasal drip is often associated with nasal congestion (stuffy nose) that makes it difficult to breathe through the nose. This nasal stuffiness is caused by swelling in the lining (mucosa) of the nasal passages. Causes of both nasal congestion and post-nasal drip include:
- Infection (viral and bacterial)
- Structural abnormalities (deviated septum)
- Environmental allergies
- Nasal polyps
- Vasomotor rhinitis (swelling of the lining of the nose with increased clear mucus drainage caused by a reflexive trigger such as cold air or some chemicals/medications)