The common reasons for coughing phlegm are as follows: 1, normal phenomenon, cough belongs to the body’s protective reflex; 2, upper respiratory tract diseases, such as bronchial inflammation, tonsil inflammation, and inflammation of the lungs caused by; 3, bronchial asthma attack, the patient will also appear chest constriction, shortness of breath, dyspnea, etc.; 4, sinusitis or post-nasal drip syndrome, which can be accompanied by nasal congestion, headache, yellow runny nose, sneezing, etc.; 5, lung infections , which can also be accompanied by high fever, chills, chest pain, cough, and sputum volume will increase significantly. Therefore, when sputum changes, you should consult a doctor in time.