Yellow nasal discharge is considered to be caused by sinusitis, acute rhinitis secondary to bacterial infection or nasal foreign body with infection. 1. Sinusitis: patients due to pathogenic microbial infection, allergic reaction and nasal sinus structure abnormalities and other reasons lead to sinus mucosal inflammatory reaction, so that the sinus cavity secretion increases, bacterial infection is mostly yellow purulent secretion, so can be seen flowing yellow nasal discharge. 2. Acute rhinitis: acute rhinitis is caused by viral infection, when secondary bacterial infection can be changed from clear mucus to yellow pus. 3. Nasal foreign body with infection: if the patient accidentally such as beans, nuts, plastic toys and other foreign objects into the nasal cavity, often can be manifested as unilateral nasal flow mucopurulent mucus, nasal congestion and blood in the snot. If the retention time is longer, it can cause bacterial infection, so that the secretion is yellow, so it can be seen flowing yellow nasal discharge. When yellow nasal discharge occurs, it is recommended to consult a doctor as soon as possible for a clear diagnosis.