Postnasal drip syndrome is a syndrome in which secretions flow backwards into the postnasal and pharyngeal regions, or even backwards into the vocal cords or trachea, due to nasal diseases, resulting in a cough as the main manifestation. It is now believed that inflammatory lesions in the nasal cavity and sinuses can stimulate cough receptors located in the nose, sinuses, and throat to produce an inflammatory response similar to that of the lower respiratory tract; at the same time, neuropeptides and neurotransmitters contained in sensory nerve endings can stimulate airway sensory nerves, thereby increasing the sensitivity of the cough reflex. In addition, in postnasal drip syndrome (PNDS), excessive secretions from the nose or sinuses drip backward into the pharynx, physically stimulating the cough afferent nerves in the pharynx and triggering coughing. A variety of diseases can cause PNDS, such as the common cold, allergic rhinitis, non-allergic rhinitis, vasodilatory rhinitis, and infectious rhinitis. The 1998 American College of Chest Physicians cough guidelines clearly state that postnasal drip syndrome, cough variant asthma and gastroesophageal reflux are the most common causes of chronic cough, accounting for 85% to 98% of the incidence. The latest Guidelines for the Diagnosis and Treatment of Cough in China also state that postnasal drip syndrome is a common cause of chronic cough. American researchers found that postnasal drip syndrome accounted for 28% to 57.6% of chronic cough patients. The diagnostic criteria for postnasal drip syndrome recommended in our Guidelines for the Diagnosis and Treatment of Cough are as follows: (1) episodic or persistent cough, predominantly during the day and less frequently after sleep; (2) postnasal drip and/or a sense of mucus adhesion to the posterior pharyngeal wall; (3) history of rhinitis, sinusitis, nasal polyps or chronic pharyngitis; (4) examination reveals mucus adhesion to the posterior pharyngeal wall and a cobblestone-like appearance; (5) cough relief after targeted treatment. cough relief after targeted treatment. Common tests to rule out postnasal drip syndrome include specialized ENT examinations and imaging examinations, such as anterior rhinoscopy, nasal endoscopy, fiberoptic rhinitis, lateral DR films of the nasopharynx, sinus CT, etc. Treatment options: Patients suspected of postnasal drip syndrome should be treated specifically based on their possible underlying disease. For PNDS caused by the common cold, non-allergic rhinitis, vasodilatory rhinitis, and year-round rhinitis, 1st generation antihistamines (e.g., chlorpheniramine maleate) and decongestants (pseudoephedrine hydrochloride) are preferred. Most patients develop efficacy within a few days to 2 weeks after initial treatment. Postnasal drip syndrome due to allergic rhinitis is effective with a variety of antihistamines. 2nd generation antihistamines without sedation are preferred, commonly used drugs such as loratadine or asmizole. Nasal inhalation of glucocorticoids is the drug of choice for allergic rhinitis, and the inhalation dose is usually beclomethasone propionate 50 μg/time/nostril or equivalent dose of other inhaled glucocorticoids once or twice daily. Sodium cromoglycate inhalation is also good for the prevention of allergic rhinitis and is applied at a dose of 20 mg/dose 3-4 times a day. Improving the environment and avoiding allergenic stimuli are effective measures to control allergic rhinitis. Allergen immunotherapy may be effective but has a long onset of action. The main treatment for acute bacterial sinusitis is the application of antibacterial drugs, and nasal inhalation of glucocorticoids and decongestants may be used to reduce inflammation when the effect is poor or the secretion is high. For the treatment of chronic sinusitis, the guidelines recommend the following primary treatment regimen: application of antimicrobial drugs effective against gram-positive, gram-negative, and anaerobic bacteria for 3 weeks; oral 1st generation antihistamines and decongestants for 3 weeks; nasal decongestants for 1 week; and nasal inhaled glucocorticosteroids for 3 months. Negative pressure drainage, puncture drainage, or surgical procedures are feasible when medical treatment is ineffective. In the treatment of postnasal drip syndrome it should be noted that not all antihistamines have the same efficacy. Current research suggests that 1st generation antihistamines and decongestants are the most effective treatment options for most patients with postnasal drip syndrome, and that 2nd generation antihistamines are likely to be ineffective for non-allergic causes of postnasal drip syndrome that are not mediated by histamine. Chronic rhinosinusitis and nasal polyps that do not respond to drug therapy should be treated with surgery as soon as possible.