When a large number of bacteria are produced in the nasal cavity, the imperial army in the blood rises to the occasion and destroys the bacteria. The battle is extremely fierce and always ends in victory for the white blood cells. However, when the body’s resistance decreases, a large number of white blood cells will die in the battlefield for fighting against the invaders, and the yellow pus is a mountain of white blood cell corpses. So when yellow snot flows in the nasal cavity, it signifies a bacterial infection. When suffering from acute rhinitis, acute or chronic sinusitis can be seen yellow pus, especially chronic sinusitis, the flow of yellow nasal discharge will be very long, up to several months, years, or even decades, distress plagued patients, very affect health. If the treatment is not timely, sinusitis further spreads to the bone causing bone marrow inflammation, such as frontal sinus osteomyelitis. In summary, yellow nasal discharge marks inflammation of the nose or sinuses, the most common being maxillary sinusitis. In addition to prolonged yellow runny nose, it also causes many symptoms, such as nasal congestion, headache, dizziness, loss of appetite, general lethargy, memory loss, low work efficiency, etc. Sometimes tooth decay can also cause the accumulation of pus in the maxillary sinus, which has a foul smell. Sometimes the pus can flow from the posterior nostril to the nasopharynx, causing discomfort in the throat. When the pus flows into the respiratory tract, it can cause coughing and in severe cases, acute and chronic bronchitis. Long-term pus stimulation in the nasal cavity can cause a series of pathological changes, such as swelling of nasal mucosa causing ventilation disorders and olfactory nerve invasion causing hyposmia, etc. Therefore, rhinitis and sinusitis should be treated in a timely manner, and more satisfactory results can be obtained with appropriate medication, symptomatic treatment or surgical treatment.