When you have a cold or the flu, mucous membranes that line the cavities of the nose produce a combination of mucus and fluid designed to fight off and wash away bacteria. The nose also produces extra mucus after exposure to an allergen, whether it is pollen, animal hair, or anything else. Crying hard can also cause excess fluid to drain from the channel in the inner corner of the lid in the nasal cavity and out through the nose.
Why does your nose run when you are out on a chilly winter day, even when you are not sick or sad?
Your nose at Work
Our noses warm and humidify - add moisture to - the air we breathe, as it moves into the lungs. So when breathing in cold, dry air, the moist tissue inside the nose automatically increases fluid production to do its job to protect sensitive lung tissue. However, when there is too much liquid, the excess tends to drip out, creating a runny nose.
Winter has other effects that make it more likely that you have a runny nose. Cold temperatures can cause water droplets inside the moist nose to join together and form large, heavy drops of water that can drip from your nostrils. And cold air also accelerates the production of mucus.
Could you have Skier nose?
Scientists have a name for a related syndrome associated with exercising outdoors in cold weather: Not surprisingly, it's called skier nose. A study in 1991 published in the journal Annals of Allergy, Asthma and Immunology found that almost 100 percent of skiers complained about runny noses while participating in their sport.
While a runny nose are annoying in almost any season, it is not harmful. And if you are worried that you get a cold from being out in the cold, do not fret. It is a common myth, but experts believe that the reason why colds are more common in winter, because we spend more time indoors around other people who transfer their cold virus to us by sneezing and leave germs on surfaces that we touch.
If you are really bothered by your winter runny nose, try taking an over-the-counter decongestant. The prescription nasal spray Ru-Tuss Atrovent and has also been shown to be effective in drying drippy noses.
So there is always the mother's advice: Before you go out in the cold, cover your nose and mouth with a scarf. Air breathed through the fabric will be warmer and wetter, which can cut down on those annoying drips.