Yellow phlegm in the throat may be related to sinusitis, upper respiratory tract infection or pneumonia. 1. Sinusitis: because of inflammatory mediators stimulate the nasal glands, secretion of mucus to increase the formation of more secretions, secretions wrapped epithelial cells, pus cells, pathogens, etc., can be accumulated in the sinuses, there is a sense of erasing the feeling of inexhaustible, or feel “phlegm” can only be inhaled into the pharynx and then spit out the back group of patients suffering from sinusitis is particularly obvious. 2. Upper respiratory tract infection: due to bacterial or viral infection, the throat wall is stimulated to produce purulent secretion, which contains epithelial cells, pus cells and other substances, and appears yellow after concentration. 3. Pneumonia: when bacteria or viruses walk down into the lungs, triggering infection, inflammation secretion of fluid and lung tissue shedding cells to produce sputum, sputum mixed with a variety of pathogens, pus cells, etc., concentrated and discharged through coughing is yellow sputum. The yellow sputum in the throat may also have other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.