'Tis the season—the season for runny noses, that is. Fall and winter are prime time for colds and flu. But did you know there are many other causes of runny noses besides cold and flu viruses? Here is your primer on why, as the old joke goes, your nose may be running (and your feet may be smelling), instead of the other way around.
What is a runny nose, really?
The nose you see in the mirror is just the outerwear of your breathing equipment. The inside of your nose is called the nasal cavity. The nasal cavity is connected to your sinuses. When your nose is working properly, your nasal cavity and sinuses serve as a filter for any potentially troublesome bits you might be breathing in.
The nasal cavity and sinuses are lined with a thin layer of mucus that works like sticky fly paper to trap things such as pollutants, allergens (dust and pollen), bacteria, viruses and other irritants. Under normal conditions, this mucus drains down the back of your throat, keeping your nose and lungs clean and free of irritants.
When your nasal passages get overwhelmed with irritants, your nasal passages may become inflamed. As they become inflamed, they produce more—and thinner—mucus. Instead of discretely slipping down the back of your throat, the excess mucus swamps the system and runs out of your nose.
The reasons behind that runny nose
There are dozens of reasons a person can develop a runny nose. Make that hundreds of reasons, if you count every single virus that can cause the common cold. There is even a medical name—nonallergic rhinopathy—for people who have a runny nose for no identifiable reason.
Usually, however, it is possible to identify the reason for a runny nose. Some of the more common reasons, as well as a few of the more unusual ones, are listed below:
- Common cold – The Centers for Disease Control and Prevention (CDC) note that a runny nose is often a symptom of the common cold. In fact, the common cold is the most common illness in the United States. Since more than 200 different viruses can cause the common cold, it is no surprise adults average two to three colds each year. Children under six experience even more colds than adults do, averaging six to eight colds per year (that's one per month during cold and flu season, beginning in September and ending in April).
- Influenza (flu) – A runny nose can also be one of the symptoms of the flu. While cold symptoms tend to be mild, flu symptoms can be more severe and lead to more serious complications. When in doubt, it's a good idea to discuss your (or your child's) symptoms with a health care professional to ensure proper treatment. (The professional staff at a CVS MinuteClinic can help you evaluate whether your symptoms warrant further medical treatment.)
- Allergies – When cold and flu season is over you can typically breathe easier because—no, wait: Welcome to allergy season. Depending on your particular sensitivities, allergy season may start in early spring (tree pollen, mold), continue into late spring (grass pollen) and last through the summer and into fall (ragweed pollen).
- Exercise – Exercise, you say? Yes, exercise can cause a runny nose in some people. This condition is called exercise-induced rhinitis. In some folks, the runny nose they get from exercise may actually be allergy-related. For example, running through the neighborhood park will expose you to more grass pollen than sitting inside your air-conditioned home. But non-allergic rhinitis, triggered by exercise, is a genuine problem for some people.
- Tear-jerkers – Have you ever watched a sad movie or closed the last page of a heartbreaking book, only to find your eyes watering and your nose running? Your tear ducts actually drain into your nose. The volume of tears you produce throughout the day to keep your eyes clean is generally too small to make a noticeable difference in your nasal mucus. Crying can increase your tear volume to the point that the excess comes running out your nose.