A runny nose may be caused by coronavirus infection or allergic rhinitis or other infectious diseases of the upper respiratory tract. 1. Coronavirus infection: Typical manifestations are fever, cough, sore throat and so on, some accompanied by abdominal pain, diarrhea and other gastrointestinal symptoms. A runny nose alone is not a typical manifestation, but the possibility of infection cannot be ruled out. Some people infected with coronavirus infection do not have any symptoms. 2. Allergic rhinitis: The typical manifestation of allergic rhinitis is sneezing and running nose. Some of them are accompanied by nasal itching and abnormal sense of smell. It is more common in spring and fall. There is often a family history of allergic rhinitis. 3. Other upper respiratory tract infections: a runny nose can be caused by other viruses such as rhinovirus and other acute upper respiratory tract infections. There may also be other diseases associated with a runny nose. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment.