The presence of a clear runny nose is a clinical symptom that requires consideration of a cold caused by a virus or mycoplasma or chlamydia infection. Due to the decrease of resistance, these pathogens invade into the respiratory tract, causing congestion, edema and exudation of inflammatory substances from the mucous membrane of the nasal cavity, resulting in the overflow of clear nasal discharge. Generally, no special treatment is needed for common cold, you can rest in bed, pay attention to keep warm and avoid getting cold, and you can completely get better within a week, especially for viral cold. For upper respiratory tract infections with mycoplasma and chlamydia, they can get better within two weeks and heal themselves. However, more serious colds require medical intervention, and for severe mycoplasma infections, macrolides and quinolones such as erythromycin, azithromycin and levofloxacin can be used. For colds caused by influenza viruses, early antiviral treatment with drugs such as oseltamivir should be used at this time.