You may have heard the old joke: If your nose is running and your feet smell, you
must be upside down! But why does your nose run? Read on to find out the whole story.
What's Running?
To understand why your nose runs, you need to know what mucus
(say: MYOO-kus) is. This is the gooey, sticky, slimy material that's made inside your
nose (also known as snot).
Believe it or not, your nose and sinuses
make about a quart of snot every day!

For something kind of gross, mucus does a lot of good. It keeps germs, dirt, pollen,
and bacteria from getting into your lungs
by stopping them in your nose. But sometimes mucus doesn't stay put.
Reasons for Running
If your nose is running, there are several possible explanations:
You have a cold
or the flu:
When you have either one of these, your nose goes into mucus-making overdrive to keep
the germ invaders out of your lungs and the rest of your body, where they might make
you even sicker than you already are. You know what happens then: The mucus runs down
your throat, out your nose, or into a tissue when you blow your nose. Or it can fill
your sinuses, which is why you get that stuffy feeling.
You have allergies:
Kids who have allergies get runny noses when they're around the thing they're allergic
to (like pollen or animal hair). That's because their bodies react to these things
like they're germs.
You're crying: When you cry, tears come out of the tear glands
under your eyelids and drain through the tear ducts that empty into your nose. Tears
mix with mucus there and your nose runs.
Baby, it's cold outside: When you're outside on a cold day, your
nose tries its best to warm up the cold air you breathe before sending it to the lungs.
Tiny blood vessels inside your nostrils open wider (dilate), helping to warm up that
air. But that extra blood flow leads to more mucus production. You know what happens
next. Drip, drip, drip.
Stoppin' the Runnin'
If you have allergies, your doctor might give you medicine called an antihistamine
(say: an-tye-HISS-tuh-meen). But sometimes the easiest thing to do is — you
guessed it — blow your nose!