Always runny nose is considered to be related to upper respiratory tract infection, vasomotor rhinitis, allergic rhinitis and so on. 1. Upper respiratory tract infections: Clear running nose can occur due to bacterial or viral infections or colds caused by the cold. 2. Vasomotor rhinitis: mostly due to autonomic dysfunction, too strong reaction to external stimuli, due to the congestion and edema of the mucous membrane in the nasal cavity, there will be an increase in the phenomenon of secretion, which will lead to runny nose. 3. Allergic rhinitis: due to allergy to certain substances, such as pollen and other factors to stimulate the nasal mucosa, can cause the mucosa of the nasal cavity suddenly reactive sensitization, secretion increase, etc., the patient will have sneezing, runny nose and other symptoms. If often runny nose, need to go to the hospital in time, clear diagnosis and standardized treatment, so as not to delay the condition.