Anyone with a stuffy nose these days can’t help but marvel at the Play-Doh Fun Factory working overtime between their ears, extruding an endless stream of … stuff.

You blow your nose and five minutes later, you need to blow it again. Five minutes later, you need to blow it again. Five minutes later, you need to blow it again. This can go on for days.

How can this be? How can an area the size of a grapefruit manufacture so much … Play-Doh?

Answer: Because our bodies are amazing, in a really gross way.

“Most people are shocked by how much mucus we make and swallow every day,” said Dr. Erin O’Brien of the Mayo Clinic in Rochester.

How much mucus?

“An estimated one to two cups every day,” she said. That’s roughly equivalent to a half-dozen of those 2-ounce bottles of hand sanitizer, a squeeze bottle of mayonnaise, a pint of home-brewed kombucha, or a decent serving of lutefisk.

This is when we’re healthy, “which means that our body is working, which is a cool thing,” said O’Brien, a surgeon in the department of otorhinolaryngology — what the rest of us call ENT, or ear, nose and throat.

Illness can increase mucus production for reasons that are both helpful and nefarious, she added. Because the body is fighting bacteria, or an allergy, or an infection, it may produce more mucus to capture these unwelcome intruders.

But O’Brien said that viruses also want to spread, and how better to do that than by spurring the production of mucus, which then gets blown into tissues, which then are handled by fingers, which then corrupt every door handle, every checkout line pen, every grip of a grocery cart. So wash your hands often.

Did we mention that you should wash your hands often?

Mostly, though, it’s not the amount of mucus that changes as much as the consistency. It lodges in our sinuses instead of benignly sliding down our throats as it normally does.

And yes, if you’ve considered this process for even a moment, it does indeed mean that we eat our, um, Play-Doh all the time, with or without a slight detour via our fingers.

(Jedi mind trick: You never read the previous sentence.)

But how? And why so much?

The “how” and “why” of mucus are inseparable: The linings of our sinuses contain glands that continuously produce mucus for two very worthwhile reasons: “Your nose is sort of a humidifier, so when you’re breathing in the dry air, the mucus warms and humidifies it before it gets to your lungs,” O’Brien said.

“Plus, mucus catches all the dust and bacteria and allergens and pollen flying through the air, so it’s like a filter.”

Sinuses have other functions. Turns out we need them like we need holes in our heads. Sinuses reduce the weight of our facial bones and skulls, while the air-filled spaces add resonance to our voices, according to the Merck Manuals, the time-honored medical reference books.

“Basically, the whole cheek is a sinus,” O’Brien said. In addition to that duo, there are two sinus cavities in our foreheads, and smaller ones between our eyes. Some are cavities, while others are more dense, like a honeycomb. All constantly produce mucus.

If you could calculate the surface area of the sinus linings, it likely would rival Lake Superior. OK, we just made that up, but when your nose is running, and you’re in a meeting, and there’s not a tissue in sight, doesn’t it feel that way?

Flushing is fine

O’Brien said people often ask how she chose this specialty, “mostly while I’m looking up their noses. But I’m a surgeon, and when people are miserable from their sinuses, and I can operate and make them feel better, it’s great.”

Sinus pain is a complex malady, but one emerging finding is that 90 percent of what people consider sinus headaches likely are migraines, “especially when they say their heads are throbbing and they blow but can’t get anything out,” O’Brien said. “Unfortunately, all those companies sell sinus over-the-counter medicines, when people should be treating a migraine.”

She’s a proponent of flushing nasal cavities with the saline rinse of a neti pot, which resembles a tiny teapot filled with saltwater that you tip into one nostril until it runs out the other. “Whenever I feel I’m getting sick, I do a sinus rinse,” she said.

Keep humming along

One last bit of nasal knowledge: In addition to mucus, sinuses also produce nitric oxide, a gas that helps kill harmful bacteria. “Yeah, who knew?” O’Brien said, laughing. The gas protects our lungs by killing bacteria before it gets too far.

Several years ago, researchers noticed that well-ventilated sinuses are healthy sinuses, and that one way to keep air moving through was by humming. Writing in the American Journal of Respiratory and Critical Care Medicine, they compared airflow in people when they hummed and when they simply exhaled.

“Specifically, they looked to see if humming led to greater levels of exhaled nitric oxide,” according to an article in the New York Times. “Ultimately, nitric oxides during humming rose 15-fold.” A European study corroborated those findings.

So to lessen the likelihood of sinus infections, researchers suggest that daily periods of humming tunes might help people lower their risk of chronic problems.

For your nasal playlist: How about “Walking in a Winter Wonderland”?