Nasal mucus often backflow into the mouth is considered to be caused by acute and chronic rhinitis, acute and chronic sinusitis and other factors. 1. Acute and chronic rhinitis: acute rhinitis late nasal congestion aggravated, increased nasal discharge; chronic rhinitis is a chronic inflammation of the nasal mucosa and submucosa, the main clinical manifestations of nasal congestion, increased nasal discharge and other symptoms; increased nasal discharge, can backflow into the oropharynx. 2. Acute and chronic sinusitis: patients with acute and chronic sinusitis may have nasal congestion, pus flow, headache and other phenomena, especially when the posterior group of sinuses (pterygoid sinus, posterior group of sieve sinus inflammation) is involved, the nasal secretion increases, and backward flow into the nasopharynx and oropharynx. In addition, there are many other reasons that can cause frequent backflow of nasal mucus into the mouth, and it is recommended that patients go to the hospital in time to clarify the cause of the disease and receive treatment as soon as possible.