A runny nose is a persistent drainage of mucus from the nose or back of the throat. It is annoying but rarely serious, and it usually goes away on its own.
 

Causes & Complications

Sometimes called rhinorrhea, a runny nose is a very common malady that affects everybody at one point or another. It can be caused by a variety of factors including colds, flu, and allergies. Cold weather, spicy foods, crying, head trauma, overuse of nasal sprays, and drug abuse and withdrawal can also trigger a runny nose.

Complications are rare, but occasionally excess mucus will block the eustachian tubes and cause an ear infection. It can also plug up the nasal passages, leading to a sinus infection. Postnasal drip occurs when mucus drains down your throat; this can cause a cough that worsens when you are lying down at night. You should see a doctor if symptoms persist longer than 10 days or are accompanied by a high fever, or if your discharge is greenish or contains blood.

 

Treating a Runny Nose

A runny nose usually clears up on its own within a few days. However, it is irritating and can interfere with your daily life. There are measures you can take to ease your symptoms in the meantime. Blow your nose often to clear it of mucus buildup, and use saline nasal sprays to moisturize your sinus cavities and help remove irritants such as pollen and dust. Increase your fluid intake, and use a humidifier to moisturize the air. Antihistamines are effective when allergies are the cause of your runny nose.

 
Further reading