Rhinorrhea – The Runny Nose - Columbia Daily Tribune

Going out into the cold requires a lot of preparation if you want to remain safe and comfortable. You put on a hat because so much heat leaves through your head; you cover your hands because your body cannot deliver warm blood there fast enough; and you bundle in layers so the trapped air insulates your body.

After all that preparation, you should be well-prepared for some time in the winter weather. However, after just a few minutes outside, your nose starts to run. There are some very clear scientific reasons for that cold and runny nose. First, the term “runny nose” is not a scientific term. The correct medical term for a runny nose is “rhinorrhea.” This word comes from the Greek words “rhinos,” meaning “of the nose,” and “rhoia,” meaning “flowing.”

Moistening the Air

Rhinorrhea is especially common during winter months and certain low-temperature seasons. Your body prefers to breathe in warm and moist air. Winter air is not only colder, but cold air holds less moisture, so the air we breathe in is much drier. Cold, dry air can be harsh on our breathing passages and lungs.

One of the purposes of our nasal passages is to warm inhaled air so it’s closer to our body temperature before it enters the main parts of our respiratory system. The body accomplishes this by producing mucus inside the nose. As the cold air travels through the nasal passages, it picks up some of the heat and moisture from the mucus. During the cold and dry winter season, the air we breathe tends to dry out our nasal passages. Your body must produce more mucus to keep the nose moist, and the colder it is, the more mucus the nose thinks it needs to produce. Your nose will quickly produce an excess of the air-warming mucus, and your nose might begin to drip.

The dry air also triggers your body to make more mucus even when it is not cold because mucus is a natural trap for germs and viruses. When the air is dry, the mucus will dry up, and the natural barrier will not work as well. Your body will try to moisten the nose by making new mucus, but sometimes the inside winter air is so dry it can’t keep up, and part of your natural defense will not work as well.

Rhinorrhea Physics

While your body is purposefully producing mucus to warm the air you breathe, some physics also is involved in producing your running nose. As discussed above, warm air holds a lot more moisture than cold air. An environmental example of this is morning dew. As warm air cools overnight, it cannot hold the same amount of moisture, and some of that moisture comes out of the air and condenses on surfaces.

The same principle of condensation is working inside your nose. When air is exhaled out your nose, water vapor condenses as the warm air meets the colder outside temperature near the nostrils. This causes an excess amount of water to build up inside your nasal cavities. After you are out in the cold for a while, enough water condenses inside your nose, gravity starts to win, and the water begins to drip out of your nose.

As disgusting as mucus might be, your body certainly depends on it, and your body certainly makes a lot of it. On an average day, your body produces about a quart of mucus. That’s a lot of mucus! However, between trapping germs and pre-treating the air you breathe, it has a lot to do. So, next time you are out in the cold and your nose starts to run, now you know that your body and physics are combining in a perfectly normal way to keep you healthy.

Mike Szydlowski is the science coordinator for Columbia Public Schools.

http://bit.ly/2LBHPOz