Have you ever wondered why your nose runs when it’s cold outside, even though you may not be sick? It turns out that mucus from your nose actually plays an important role in protecting sensitive lung tissue, by warming up the air you inhale so that it reaches your body temperature. In cold, dry environments this mucus dries out quickly, resulting in your nose producing extra mucus by increasing blood flow to the nose.

Additionally, the air that you exhale when you are outside during the winter is warmer than the surrounding cold air. As a result, this warm air will condense on the surface of the nose and change from water vapor into liquid water. The water that comes from the air you exhale will run out of the nose along with the increased production of mucus. These are some of the reasons why cold weather causes runny noses.

Click here to learn more about the science behind cold weather and runny noses!