Cold with clear nasal discharge followed by yellow nasal discharge is clinically commonly caused by the invasion of pathogens such as viruses, which leads to a decrease in resistance and secondary bacterial infections. Due to the exudation of inflammatory substances from the mucous membrane of the respiratory tract, viral infections are clear-colored secretions, while bacterial infections appear as yellow-purulent secretions. At this time, blood tests can be done, and if necessary, nasal discharge can be taken for culture of pathogens and drug sensitivity test to clarify the cause and anti-pathogen treatment. Anti-viral drugs such as ribavirin and oseltamivir can be used, and anti-bacterial drugs such as penicillins and cephalosporins can be chosen.