Children coughing and running yellow snot may be caused by sinusitis, allergic rhinitis combined with infection or colds. 1. Sinusitis: If the nasal cavity is infected by pathogenic bacteria, such as purulent coccus, it may induce inflammation and infection of the mucous membrane of the sinuses, resulting in sinusitis, which will lead to recurrent coughing, accompanied by yellow nasal discharge, headache and other symptoms. 2. Allergic rhinitis combined with infection: frequent contact with mold, dust mites or pollen and other allergy-prone substances in life may induce allergic rhinitis, postnasal drip caused by patients with cough, and concurrent infections accompanied by yellow nasal discharge and other symptoms. 3. Colds: when the nasal cavity or throat acute inflammatory infections, may induce colds, colds will lead to patients with cough, yellow nasal discharge and other symptoms. Children coughing and running yellow snot, there are other reasons, need to go to the hospital to do the examination, according to the cause of treatment.