Streaming yellow snot is almost ready, usually asked after the cold from clear nasal discharge to yellow nasal discharge, can not judge the severity of the disease only by the color of the nasal discharge. Cold running yellow snot at the same time, if the amount of snot is small, there is no other uncomfortable symptoms, is almost well. On the contrary, the cold is serious. When the virus invades the human body, the symptoms of upper respiratory tract infection, nasal mucosa congestion and edema, mucous glands in the mucosa by inflammation, mucus secretion increased, the symptoms of clear nasal discharge, accompanied by cold, nasal congestion, sneezing, coughing and other symptoms. At this time, the body’s immune system will start the defense behavior, neutrophils will phagocytosis of viruses that invade the body, neutrophils contain hypochlorous acid, hypochlorous acid is produced by the neutrophil myeloperoxidase, myeloperoxidase is green. When the nasal mucus from the clear to yellowish green, and the amount is also very small, the human body than the early stage of the cold state of mind is good, that is, the cold is almost well. If the cold turns from clear nasal mucus into yellow nasal mucus, the amount of nasal mucus is more than clear nasal mucus, accompanied by fever, loss of appetite, mental depression and other symptoms, indicating that the cold is infected by a combination of viruses and bacteria, and it is a worsening of the cold. In this case, we should go to the hospital in time to see a doctor, symptomatic treatment, so as not to miss the disease.