Runny nose is the phenomenon of increased nasal secretion, under normal circumstances, the nasal cavity is covered by the nasal mucosa, nasal mucosa has a large number of glands, through the secretion of the glands in the nasal mucosa, the nasal cavity can be secreted every day about 1,000mL of liquid, under normal circumstances, these liquids are able to uniformly by the cilia transport system to deal with the role of heating and humidification of the nasal cavity, so you can not feel the phenomenon of runny nose. When suffering from rhinitis, sinusitis and stimulation, such as emotional changes, body surface cold, heat will be increased nasal secretion phenomenon, will feel the nasal cavity runny nose. In addition, when there is a traumatic stimulus or eye tears and other secretions increase, there will also be liquid flow into the nasal cavity to appear the phenomenon of increased nasal discharge.