Patients with yellow phlegm in the nose, mainly due to purulent nasal discharge in the nasal cavity, often occur because of inflammation of the sinuses, which often occurs after a cold or secondary to allergic rhinitis, acute rhinitis, and other conditions. When bacterial infection occurs in the sinus cavity, it is easy to further develop inflammatory purulent secretions that drain into the nasal cavity through each sinus orifice, resulting in purulent nasal discharge, and some patients may also have purulent nasal discharge flowing backward into the throat, resulting in repeated coughing and spitting out thick sputum, which requires targeted and active use of antibiotics for treatment.