A runny nose, also known as rhinorrhea, is a condition where there is an excessive flow or discharge of mucus from the nasal cavity. This can be caused by various factors such as infection, allergies, cold weather, hormonal changes, and certain medical conditions. The mucus is produced by the nasal membranes to trap and remove dust, pollutants, and other irritants from the air we breathe. However, when there is an excess of this mucus, it can drip down the back of the throat causing irritation or even loss of sleep due to constant wiping. A runny nose is usually a symptom of another condition and should be treated accordingly under the guidance of a healthcare professional.