Usually in the case of cold or rhinitis, when the bacteria invade the human body, there will be yellow nasal discharge, so yellow nasal discharge is usually the liquid secreted by the mucous membrane in the nasal cavity, and then infected with bacteria or inhaled dust, so there will be sticky thick secretion out. If infected by bacteria, it will be obvious that the nasal discharge becomes sticky and yellow in color, which is mostly septic bacterial infection, such as Gram-positive cocci and Gram-negative bacillus infection, there will be yellow nasal discharge, and there is usually a bad smell in the nasal cavity. On the other hand, in the case of viral infections, the nose is usually white and there is usually no odor in the nasal cavity.