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August 10, 2016

Infrequently Asked Questions: Why is mucus so slippery?

During peak allergy and cold season, it's not totally uncommon to look down into your tissue and wonder how such a strange substance can seep from your body.

What's the deal with mucus, exactly? That's what one curious PhillyVoice reader wanted to know, and naturally, we vowed to dig around for some answers. Here, Dr. Gurston Nyquist, an otolaryngologist at Jefferson University Hospital, explains why mucus — snot — has such a slippery texture. 

Why is mucus so slimy or slippery? There’s nothing else in the body quite like it, in terms of consistency.

So, the mucus is made by the lining of the nose, and it contains proteins that are sticky to trap bacteria, viruses and molds that prevent infection and keep particles from getting lower in the airway into our lungs. It’s purposely sticky to try [to] snatch all of the infectious material before it can cause a problem.

And also, it helps keep the lining of the nose and the mucus membranes moist, so that there’s no crack in the barrier for infection or bacteria to get in.

Why is it so protective of the nose in particular? Why not our throat?

  • The world is full of questions we all want answers to but are either too embarrassed, time-crunched or intimidated to actually ask. With Infrequently Asked Questions, we set out to answer those shared curiosities.

There are all types of different mucus. There’s mucus that's a little different from what’s in the mouth, from what’s in the gastrointestinal system, on the lungs, and so all of the membranes lining the inside of the body produce mucus and the ones in the nose are a little unique in the types of proteins they have. And are a bit more sticky than the rest of the mucus membranes elsewhere in the body.

What is one thing people tend to misunderstand about their mucus or the production of it?

One of the biggest things misunderstood is that an increase in mucus may always mean a bacterial infection. Lots of things can cause increased mucus production – sometimes it can be allergies, sometimes it can be your diet, sometimes it’s a virus. We can’t always assume because someone is producing a lot of mucus that it’s a bacteria.

Right. I assume the worst.

In the winter time, for example, with the cold weather, we have lining in our nostrils with little hair-like cilia that help get the mucus down the nose and into the throat. So we swallow about a liter of mucus from the nose and sinuses a day, but with cold weather, the cilia are compromised and so the mucus just runs down the front of your nose.

Is it actually bad to be swallowing that?

No. We swallow mucus all day long and so that’s where it goes, and we produce about a liter of it.

Is that a lot?

It’s quite a bit, but it’s a small amount consistently throughout the 24 hours and you don’t normally notice it except when the production is excessive. During an infection, more mucus is produced in order to help fight the infection.

And what happens to that liter?

You swallow it, it goes into your stomach, and you don’t even realize, really, that it’s happening.

Anything to add that folks may not know?

I would say most of the time the color of the mucus is clear, and then when it turns yellow, it turns yellow because neutrophils are attracted to the area [to fight infection] when there’s a virus or bacteria, and they have a heme component to them. And that has iron. And it’s the heme and iron component of the neutrophils, and what they release in order to fight infection, that makes mucus yellow.

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