Runny nose is mainly seen in the following cases: 1. Allergic rhinitis, in addition to runny nose, patients have allergic manifestations such as sneezing, itchy nose, decreased sense of smell and itchy eyes. It can be seasonal or perennial. 2. Acute rhinitis, also known as common cold, is mainly due to viral infection inducing patients to have swollen nasal mucosa and a large amount of clear nasal discharge in the nasal cavity, patients can be accompanied by dizziness, headache, fever, general malaise, muscle aches, decreased appetite, etc. 3. Some patients have cerebrospinal fluid rhinorrhea and can have clear nasal discharge in the nasal cavity, clinically doing nasal endoscopy, sinus CT examination can find the place of cerebrospinal fluid nasal leakage, so as to make a judgment. If patients often have clear nasal discharge, they need to combine with the patient’s symptoms and auxiliary examinations for comprehensive judgment and treatment.