Postnasal drip has a certain relationship with sinusitis, but not necessarily sinusitis, rhinitis can also be caused. 1. Postnasal drip syndrome refers to rhinitis or sinusitis patients nasal inflammatory secretions, through the posterior nostril into the nasopharynx, oropharynx, hypopharynx, the pharyngeal mucosa caused by irritation, triggered by pharyngeal discomfort, is one of the important causes of chronic cough. 2. When there is sinusitis, due to the anatomical structure of the sinus-oral-nasal complex, sinusitis is easily caused by nasal discharge through the posterior nostrils into the pharynx, stimulating the emergence of coughing, coughing up phlegm and other symptoms. 3. When there is rhinitis, the mucous membrane of the nose and the inferior turbinate are congested and edematous, and the secretion of the glands is increased, which can easily lead to the accumulation of mucous or purulent secretion in the nose, and part of the secretion will flow into the pharynx, which will lead to cough and other uncomfortable symptoms. Postnasal drip syndrome is commonly associated with rhinitis and sinusitis, and those with these diseases are advised to consult a doctor in time to find out the cause of the disease and carry out targeted treatment.