Believe it or snot: nasal mucus vital to maintaining health

A woman is silhouetted as she uses a tissue to blow her nose in Toronto on Friday, November 21, 2014. (CP / Nathan Denette)

TORONTO -- It's icky and messy and sometimes it clogs your airways, making you feel like you can't breathe. Heck, even its name is repugnant.

We're talking about snot here.

Yeah, gross topic. But with cold and flu season looming, snot -- or nasal mucus, as it can be more delicately described -- is something many of us will experience first hand in the not-too-distant future.

Here are some things you may not know about this decidedly disgusting bodily fluid:

Let's start with what might be a startling fact. We all produce quite a lot of nasal mucus every day. How much? Between one and two litres, experts say.

That's right. One to two litres. Every day. If you are having a hard time picturing that, think about the milk cartons in your fridge.

Snot is what's known as the mucus blanket of the mucus membranes of the nasal passages and the sinuses. For those tissues to do their jobs properly, they need nasal mucus.

The nasal passages are actually lined with tiny little hairs called cilia, explains Dr. John Lee, a head and neck surgeon at Toronto's St. Michael's Hospital.

Nasal mucus sits on top of those hairs, keeping them moist so they operate properly. It also humidifies the air we breathe in.

As well, the mucus is like a fly paper strip. Impurities in the air you draw into your nasal passages -- things like dust, pollens, and other debris -- stick to the mucus so they don't get into your lungs.

Those little hairs, the cilia, wave in a conveyor belt motion, moving the mucus towards the back of your nasal passages and into your throat. You swallow it and the gastric acids in your stomach neutralize anything the mucus is carrying. This is something you do all day, every day.

Yeah, still gross. But try to think of it this way: This is one of the basic weapons in your body's protective arsenal. This stuff is keeping you healthy.

Nasal mucus is made by glands in your nasal passages -- goblet cells, to be precise. It's mostly water -- 95 per cent in fact, says Lee. The remaining five per cent is made up of proteins, salts and cells from the immune system.

Most of us don't think about snot unless something happens to increase the amount of it that we produce or we become aware of changes to its colour or viscosity. Our noses start running. A tissue captures a thick gob of yellow goo. We feel like we're swallowing wads of chewing gum.

When we are infected with something that triggers a cold -- generally a virus -- our production of nasal mucus increases. Depending on how bad the cold is, we can feel like we're drowning in gallons of snot -- like we'll be blowing our noses forever.

"Whether we go from one to two litres to gallons, I think that might be a bit of a stretch," says Dr. Allan Vescan, a head and neck surgeon at Toronto's Mount Sinai Hospital.

"But there's definitely some quantifiable increase. And then because the properties of it change -- it's not the normal, clear, viscous mucus, it becomes thicker, it can become discoloured for various reasons and there's more of it -- that's when you start to feel it and notice it more."

So what's going on when that happens?

The immune system responds to the invasion by sending more blood to the tissues in your sinuses and nasal passages. Those tissues swell as a result, contributing to the feeling of congestion, Vescan says.

White blood cells, a critical component of the immune system, also move into the area. This inflammation of the nasal tissues stimulates increased production of nasal mucus and changes the quality of what comes out when you blow.

Some of the enzymes produced when white blood cells break down contribute to the change in colour you might see in your nasal mucus during a cold, Vescan says. It may become yellow, or even greenish.

Both Lee and Vescan say some patients read those changes as a signal, thinking coloured mucus is evidence of a bacterial infection that may require treatment with antibiotics. But that's not necessarily so.

"Discoloured mucus is definitely a sign of something happening. And yes, patients do interpret discoloured mucus as infection and often think it needs an antibiotic," Vescan says.

"But we don't use the colour of the mucus as our guide for when to give antibiotic. It's usually the amount of time the patient has had symptoms and the severity of the symptoms that will often guide that."

Lee says the rule of thumb is that if nasal mucus remains discoloured for seven days or longer -- especially if the colour gets deeper -- then suspicion grows that a bacterial sinus infection may be at work.

"At that point I would say it's worthwhile seeking medical attention to consider whether you do in fact have a sinus infection that might require antibiotic treatment," he says.

Otherwise, the options are relatively limited. You can keep plenty of tissues handy. You can use a saline nasal spray or a nasal rinse.

"Saline lavage or douching of the nose is something that we highly recommend," says Vescan.

Gross? Maybe. But apparently the technique is very effective for alleviating the symptoms of congestion. Just remember to use distilled or boiled water. A few years ago a Louisiana woman died when she developed a brain infection after using contaminated tap water for a nasal rinse.

Lee says nasal decongestants can be used, but with caution. The products, which are sold over-the-counter, should not be used for longer than a few days, he says.

"Beyond that, you've got to be careful because prolonged use can cause both rebound and also more deleterious effects to the lining and the health of the nose and the sinuses. The lining of the nose does not like being decongested constantly."