From the perspective of Chinese medicine, the most common factor is excessive deficiency of the body, especially when the lung is deficient cold and wind evil invade the body will lead to excessive phlegm in the nasal cavity. From the perspective of Western medicine, the most common factor is infectious factors such as bacteria, viruses or other pathogenic microorganisms that infect the human body will localize in the nasal cavity, so there will be localized phlegm, secretions and sticky secretions. If the sputum is light in color, it is a wind-cold type of infection, and if the sputum is yellow and thick, it is a wind-heat type of infection. From the Western medicine point of view, if the phlegm in the nasal cavity is thick and yellow with an elevated body temperature of 38.5°C or more, it is usually a bacterial infection, while if the phlegm in the nasal cavity is thin and clear, it is a viral infection.