11 years old with yellow pus nasal mucus may be due to upper respiratory tract infection, allergic rhinitis combined with bacterial infection or sinusitis and other reasons. 1. Upper respiratory tract infection: The upper respiratory tract infection is caused by the child catching a cold or flu. Upper respiratory tract infections usually start with a clear runny nose, and as the disease progresses, some children will experience a yellowish pus runny nose. 2. Allergic rhinitis combined with bacterial infection: Simple allergic rhinitis is often characterized by a clear runny nose, but if the child’s resistance is lowered, it may lead to a combined bacterial infection, which can turn the nasal discharge into a yellowish-pus nasal discharge. 3. Sinusitis: in acute or chronic sinusitis, due to the location of the sinuses is relatively deep, inflammation control is relatively difficult, often appear to flow yellow pus nasal discharge. 11-year-old yellow pus nasal discharge, it is recommended to consult a doctor in a timely manner, with the help of a doctor to clarify the cause of the disease, and targeted treatment or treatment.