7 Facts About Mucus, Phlegm, and Boogers

Snot is simply the everyday term for mucus produced in your nasal passageways, where it acts like flypaper to trap inhaled germs, allergens, and dust before they can cause harm. In addition to being sticky, snot is loaded with antiviral and antibacterial proteins that fight off germs, according to research.

“Snot’s purpose is to keep the lining of the nose moist,” explains Spencer C. Payne, MD, an associate professor of otolaryngology at the University of Virginia School of Medicine in Charlottesville. “The drier the lining, the more prone you are to infection.”

Picking snot and boogers out of your nose is frowned upon in most cultures, but that’s not the only reason to abstain. Nose picking, especially when it’s chronic (a condition called rhinotillexomania), can injure the delicate lining of the nostrils, causing inflammation and bleeding, and raising the risk of respiratory infections, according to a detailed case report. Better to blow snot and boogers out of your nose and into a tissue.

Sneezing is a protective reflex response to an irritation inside the nose due to any number of triggers, such as a respiratory infection, allergens, smoke, pollution, perfume, cold air, and even sudden exposure to bright light, according to a research review.

Trouble is, sneezing can spread germs. “Sneezes travel 30 to 60 miles an hour, and can fly 30 feet through the air,” Dr. Payne says. Fortunately, most colds aren’t transmitted through the air alone. “Your risk goes up if you touch a surface with germs and then touch your face,” he says. In other words, you can also get sick through contact with an infected person’s snot. The best ways to reduce that risk are to wash your hands frequently with soap and water for 20 seconds or to use an alcohol-based hand sanitizer, according to the Centers for Disease Control and Prevention. It’s also wise to steer clear of people who are sick if you can.

“Your nose and sinuses make a liter of mucus a day,” Payne says. At just under 34 ounces, that’s a lot of snot and phlegm. (For reference, a Big Gulp has 32 ounces.) “When you get a cold, [that amount] goes up even higher,” he says, and it takes longer to get rid of the extra mucus. Here’s why: When you’re sick, the tiny hairs (cilia) that move back and forth to push mucus out of the sinuses and nose become inflamed, explains Payne, and this slows down the flow. More mucus plus slower clearance equals more cold misery and lots more tissues.

If your boogers and snot are green, you have a bacterial infection, right? Wrong. That’s a booger myth, not a fact, says Len Horovitz, MD, a pulmonary specialist and instructor at Weill Cornell Medical College in New York City.

As Dr. Horovitz explains, when cold germs first infect the nose and sinuses, we make clear mucus to wash them out. After two or three days, your immune cells fight back with a substance that can change the color of your mucus to a white or yellow color. Mucus may also change to a greenish color when it thickens, which is normal, Horovitz says.

Adults get an average of two to four colds a year, mostly between September and May, and young children catch an average of six to eight colds a year, according to the American Lung Association. The body responds to the virus that causes a cold by making mucus — and lots of it.

There are no antiviral medications for treating the common cold, and antibiotics are only useful if a cold leads to a secondary bacterial infection. In other words, “don’t rush to antibiotics,” says Satish Govindaraj, MD, an associate professor of otolaryngology and chief of the division of rhinology at Mount Sinai in New York City.

Overuse of antibiotics can lead to the development of new strains of bacteria that are resistant to these medications. So if you later develop a bacterial infection and really need them, antibiotics may not work for you.

Antihistamines can also make things worse before they get better. “They will make the mucus thicker and harder to drain,” Dr. Govindaraj says. Instead, he suggests that you try an over-the-counter expectorant like guaifenesin (Mucinex), which breaks up and thins mucus in the chest and throat so that it is easier to cough up and expel.

Snot dried by the air becomes a squishy or crumbly booger that many people — especially young kids — like to pick out of their nose and eat. And as yucky as those slimy snacks are, they’re not a danger to your health.

“Truthfully, you’re eating your mucus all the time,” explains Jonathan Auth, MD, a pediatrician at CHOC Children’s, a pediatric healthcare system based in Orange County, California. “Microscopic hairs lining your nose called cilia are constantly sweeping mucus to the back of your throat, and you then swallow it. You’re also coughing mucus up out of your lungs and swallowing it all the time — the medical term for that is pulmonary toileting — to keep it from building up in your airways and becoming obstructive.”

Mucus produced by your lungs and respiratory system is called phlegm.