The most common cause of runny nose is acute rhinitis caused by viral infection, also known as cold and flu. The mucous membranes become congested and swollen when stimulated by the virus, resulting in increased secretion and symptoms such as clear runny nose and sneezing. Treatment with antiviral drugs and mucosal decongestants will soon lead to improvement. If the symptoms of runny nose are more than one week, it is not just a cold, but may be rhinitis. Rhinitis is mainly caused by the stimulation of environmental factors, allergic factors, and the decrease of body immunity, etc. The increased secretion of inflammatory media in the nasal mucosa will lead to more nasal secretions. Treatment requires the use of nasal sprays, pro-discharge drugs, or oral anti-allergy drugs.