The main causes of yellow nasal discharge in babies include: respiratory tract infections, chronic rhinitis and so on. 1. Respiratory tract infection: mostly due to bacterial infection. Bacteria will invade the mucous membrane of the respiratory tract and cause an increase in secretions, which will make the nasal mucus appear yellow, accompanied by coughing, nasal congestion and other manifestations. 2. Chronic rhinitis: If the symptoms of yellow nasal discharge last for a long time and recur, it is considered that it may be caused by chronic rhinitis. As the nasal mucus exists in the nasal cavity for a long time, the water will be absorbed by the mucous membrane of the nasal cavity, which will cause the nasal mucus to become sticky and yellow phenomenon. As you can see, if your baby has yellow nasal mucus with other uncomfortable symptoms, it is recommended to consult a doctor in time for symptomatic treatment. Meanwhile, in daily life, babies are advised to drink more water.