But after we started chatting, I discovered that the stuff actually serves a pretty important purpose in the body. Here's everything we know about what makes us hack up mucus, when you should head to the doctor — and how to clear up a wet, rattling cough faster, so you can stop grossing out everyone within earshot.
Wait — what is mucus?
“Mucus is made of about 95 percent water, with some proteins and lipids, which give it the mucus texture,” Dr. Cennimo explains. It’s secreted all throughout the respiratory system — the mucus you cough up is pretty much the same thing as snot, he says — and it acts like a protective layer, keeping the cells in your respiratory tract from drying out so they can function properly.
Phlegm also traps the bacteria, virus particles, dust, pollens, and other microbes and debris you may breathe in before they can enter your lungs, where they could lead to inflammation and damage.
“Before they get down into alveoli — the air cells deep in the lungs that allow for the gas exchange into the blood — the microscopic particles get trapped in the mucus,” Dr. Cennimo says. Think of the slick film like the Roomba of your respiratory system.
Why am I coughing up mucus?
You're clearing out all that microbe-laden mucus! Microscopic, hair-like bodies on the cells that line our respiratory tract, called cilia, use a wave-like motion to sweep the mucus back out, triggering coughing, Dr. Cennimo says. To stick with the Roomba metaphor, this process is like emptying the vacuum bin when it's full.
The reason you may feel especially bothered by it when you're sick is because you're probably producing more phlegm than usual. On average, we make about 15 milliliters — about half an ounce — of mucus every day, but when you’re sick the body can produce ten times that, Dr. Cennimo says.
It makes sense: When you're ill, your body is being assaulted by more microbes that need trapping. “Inflammation triggers the mucus-producing cells to work harder, so you have more to cough up," Dr. Cennimo explains. Most wet coughs occur when you're sick with illnesses like the flu, bronchitis, or pneumonia, according to Harvard Health. But they can also be from more long-term issues like postnasal drip.
Do color and texture of mucus matter?
Though you may have heard that green snot is a sign that you're sick, Dr. Cennimo says that medical literature has shown a clear correlation between mucus color and different health issues.
Even if you're healthy, Dr. Cennimo recommends seeing a doctor if you notice a change in the color of your regular mucus color — if it's always been white, then suddenly is green, for instance.
Texture can be informative too. In general, mucus is thicker and stickier when you’re sick, since it contains more immune cells and germs then, and thinner when you’re healthy, reports Medical News Today. (Other factors, including dehydration, can also cause thicker-than-average phlegm.)
How do I stop coughing up mucus?
But Dr. Cennimo suggests seeing a doctor any time you start coughing up mucus, since it's a pretty strong indicator that you're sick. And definitely make the visit if the symptoms persist for more than three or so days and they’re hindering your sleep and work life.