Why Oh Why Is There Phlegm?

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Phlegm can give clues to what’s going on inside. But as with so many things phlegmy, mysteries remain. Alex Reynolds / NPR hide caption

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Alex Reynolds / NPR

Phlegm can give clues to what’s going on inside. But as with so many things phlegmy, mysteries remain.

Alex Reynolds / NPR

Struggling through a nasty round of bronchitis with little better to do than binge watch Netflix and feel epically sorry for myself, I pondered the ageless cold-and-flu-season question: Phlegm. Why?

It begs an answer. The human body is capable of such constant wonder, so much to awe and inspire. And then, phlegm. And not just a little phlegm. Gobs. It’s the only word that really describes the whole phlegm experience.

So I started asking around, and in so doing have learned that there’s a lot more to phlegm than meets the Kleenex.

First, some definitions. Phlegm is really just one form of mucus, which the body produces all over the place to perform useful tasks, says Murray Ramanathan Jr., medical director of otolaryngology head and neck surgery at Johns Hopkins Medicine in Bethesda, Md. And because he suffers from chronic sinusitis himself, he gets the whole mucus thing on a pretty personal level.

“The entire lining of the respiratory tract, which includes the nose all the way to the bottom of the lung, makes mucus,” he says. Phlegm, he says, is limited to mucus made in the lung and in the trachea.

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Or as Mark Rosen, a pulmonologist at Mount Sinai in New York and a past president of the American College of Chest Physicians, puts it: “Phlegm is something you cough up, not something you blow out.”

When everything is running smoothly, we produce phlegm and mucus every day — about a liter, Ramanathan says. We usually swallow that daily production without even noticing.

Both mucus and phlegm act as general maintenance and cleaning mechanisms, keeping airways moist and tidy and defending against the host of pollutants, particles, viruses and other things that do not belong in your nose or lungs.

“That’s often what you see when you blow your nose,” says Ramanathan, who studies the role of pollutants and environment in respiratory issues. “In foreign countries where diesel exhaust is a major contributor to air pollution and some people use wood fires indoors for cooking, you actually see black deposition and particles from the air pollution.”

But mucus also has an immunological role in sniffing out trouble. It provides proteins that are antiviral and antibacterial. Receptors on the epithelial cells in the airway sense threats and create bug-fighting enzymes in the mucus, which moves along via the cilia—microscopic hair-like structures that can provide propulsion to help eject the foreign substance.

What we call smoker’s cough, Ramanathan says, “is when the components of cigarette smoke get into the lung and cause mucus [and phlegm] to be produced, because cigarette smoke is an irritant to the respiratory lining in both the nose and the lung.”

This primary defense system can be overwhelmed by viruses, bacteria and the resulting inflammation of the airway. That’s when mucus and phlegm production go into overdrive. And often with the increase in quantity, the quality changes too, becoming thicker to better trap and remove the offending material. Before you know it, you’ve achieved gobs status.

Sometimes phlegm can morph from its usual clear to yellow or green, a byproduct of the white blood cells that have charged in to fight infection. And then we as patients get asked that question — What color is it? — since color can sometimes, although not always, indicate the presence of infection.

As someone who tries to avoid inspection of my own snot or phlegm, I’ve always found this a rather disgusting query. But Ramanathan sees it another way. “As a sinus doctor, one of the worst nightmares you get is when people bring into the office the little Ziploc baggie of, ‘Look what I coughed out yesterday!’ In rare cases, they bring in Tupperware.”

So what to do to survive the phlegm stage, besides stock up on tissues and make sure the iPad is fully charged for the Netflix binge? Antibiotics will only help if you have a bacterial infection, and the average cold, no matter how phlegmy, usually doesn’t qualify.

“Just because your phlegm is green doesn’t mean you need antibiotics,” Rosen says. “Your cold and mine, even if you’re coughing up stuff, is usually viral, and there are no antibiotics for a virus.”

If your phlegm gets too gob-like (technical term), over-the-counter meds like Mucinex can help thin it, which makes it easier to expel, Ramanathan says. For the sinuses, using a Neti pot or decongestants can aid the mucus flow, and bending over a pot of steaming water helps some people with the symptoms, he says. I can revert straight to my childhood with the scent of Vicks VapoRub, doubling the comfort factor. And of course, chicken soup.

Eventually, as the illness subsides and the airway calms down and is no longer irritated (phlegmatic, you could say), the system goes back to producing our regular ration of mucus. Something for which we should be grateful every day.

Poet and journalist Wendy Mitman Clarke last wrote for Shots about giving children a bedtime pass. She has contributed to Smithsonian and other magazines.