The pharynx is both part of the upper respiratory tract and part of the upper gastrointestinal tract. The mucus glands under the mucous membrane of the respiratory tract secrete a small amount of secretion, which has a warming and moisturizing effect on the inhaled air. Normally, there is no phlegm in the throat. Under normal circumstances, a small amount of secretions and small particles inhaled from the air are sent to the pharynx to swallow or spit out through the movement of cilia on the respiratory mucosa, and the phenomenon of phlegm in the throat generally does not exist. When the respiratory tract is stimulated by various factors, resulting in inflammation and congestion of the mucous membrane and increased secretion of glands, the phenomenon of phlegm will appear. The sputum is caused by both respiratory tract diseases and upper gastrointestinal tract diseases. Such as inflammation of the nasal cavity and sinuses, resulting in the backflow of nasal secretions into the throat and causing phlegm; it is also possible that the lower respiratory tract infection causes coughing phlegm; and it is also possible that the phenomenon of phlegm in the throat caused by gastroesophageal reflux disease. If phlegm is caused by nasal reflux, it is often accompanied by an increase in nasal mucus. If the phlegm is caused by lower respiratory tract disease, it may be accompanied by coughing and phlegm symptoms. If the sputum is caused by gastroesophageal reflux, it is often accompanied by acid reflux, belching and dry vomiting. When there is excessive phlegm, it is necessary to visit the otolaryngology department to clarify the cause of excessive phlegm in order to treat it effectively.