Yellow nasal discharge after recovering from cold is mainly due to the decrease of resistance and inflammatory reaction of upper respiratory tract mucosa caused by viral infection, although viral infection is a self-limiting disease and can improve within 3-5 days. However, as the resistance decreases, purulent bacterial infection will develop, causing a large amount of yellow purulent secretions to exude from the mucous membrane of the airways, such as the nasal mucosa, and manifesting as the exudation of yellow nasal discharge after the cold has improved. Clinically, it is common to see acute attacks of chronic rhinitis and acute rhinitis, which are mainly caused by purulent bacterial infections.