Sometimes snot might seem like your worst, and most disgusting, enemy. But it’s actually your friend — helping clear the source of irritation or infection out of your system.

Snot gets a bad rap. It’s sticky and gross. And when you’re sick, it can stuff up your nose. But snot is actually your friend. It’s an important part of the immune system that keeps you healthy.

When you inhale, the snot in your nose traps dust, pollen and germs in the air that could irritate or infect your lungs. Tiny, hairlike structures called cilia move that mucus toward the front of the nose or the back of the throat. The mucus can then be blown into a tissue. Or, it can be swallowed and broken down by stomach acid. Swallowing snot might sound disgusting. But your nose and sinuses produce about a liter (a quarter of a gallon) of snot each day. Most of that slime slides down your throat without you even noticing.

Of course, allergies or a cold can kick your body’s mucus-making into overdrive. That extra snot can be annoying. But it helps your body flush out the source of irritation or infection. Inhaling tobacco smoke or getting water up your nose can trigger a runny nose for the same reason.

Mucus isn’t just found in the nose. This goop covers every part of the body exposed to air but not protected by skin. That includes the eyes, lungs, digestive tract and more. Like snot in the nose, this mucus keeps these areas moist. It also traps viruses, bacteria, dirt and other unwanted substances. Mucus in the lungs is called phlegm. If pathogens make it through your airways to the lungs, those pathogens can get stuck on phlegm. Coughing helps hack that phlegm up.

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Other animals produce mucus, too. Some, like humans, use mucus to protect themselves. Hellbender salamanders, for instance, are coated in mucus that helps them slip away from predators. That led to their nickname: “snot otters.” This mucus also fights off fungi and bacteria that could make snot otters sick.

For other creatures, mucus is more of a weapon than a shield. Sea creatures called hagfish squirt mucus at predators to clog their gills. Some jellyfish use a similar tactic. They sling out globs of stinging snot for long-range attacks against other animals. Mucus may also help dolphins make the clicking noises they use to hunt down prey. However an animal uses their mucus, one thing is certain. The power of snot is certainly nothing to sneeze at.

Explainer: The benefits of phlegm, mucus and snot Mucus might seem gross, but it actually plays a key role in the immune system that keeps you healthy. (2/20/2019) Readability: 6.0

Snot may be key to dolphins’ tracking of prey Mucus may help dolphins make the chirpy clicking noises they use as sonar to catch prey. (5/25/2016) Readability: 7.9

Secrets of slime Hagfish shoot snotty slime at predators that is so strong, it could inspire new bulletproof vests. (4/3/2015) Readability: 6.0

Orca snot leads to a whale of a science-fair project

Ouch! Jellyfish snot can hurt people who never touch the animal

Good germs lurk in gross places

This tube worm’s glowing slime may help sustain its own shine

For coughing up phlegm, water is key

Ah-choo! Healthy sneezes, coughs sound just like sick ones to us

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Ever wonder how far a sneeze can blow your boogies? A simple experiment uncovers the spray distances of different kinds of snot. Find the recipe for fake snot and instructions for the experiment in Science News for Students’ Experiments collection.

bacteria: (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth.

cilia: (singular cilium) Small hairlike features that occur on the surface of some cells and larger tissue structures. They can move and their wavelike motion can propel liquids to move in a particular direction. Cilia play an important role in many biological functions throughout the body.

digestive tract: The tissues and organs through which foods enter and move through the body. In people, these organs include the esophagus, stomach, intestines, rectum and anus. Foods are digested — broken down — and absorbed along the way. Any materials not used will exit as wastes (feces and urine).

dolphins: A highly intelligent group of marine mammals that belong to the toothed-whale family. Members of this group include orcas (killer whales), pilot whales and bottlenose dolphins.

fungi: (sing: fungus) Organisms with one or more cells that reproduce via spores and feed on living or decaying organic matter. Examples include mold, yeasts and mushrooms.

germ: Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

gills: The respiratory organ of most aquatic animals that filters oxygen out of water. Fish and other water-dwelling animals use gills to breathe.

hagfish: Slimy, eel-shaped fish without hinging jaws, whose skeletons are made of bendy cartilage rather than hard bone, and with eyes far simpler than those of other fish. Like lampreys, they are considered to be “living fossils” similar to the early relatives of vertebrates that lived hundreds of millions of years ago.

immune system: The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

infection: (v. infect) A disease that can spread from one organism to another. It’s usually caused by some type of microbe.

mucus: A slimy substance produced in the lungs, nose, digestive system and other parts of the body to protect against infection. Mucus is made mainly of water but also includes salt and proteins such as mucins. Some animals use mucus for other purposes, such as to move across the ground or to defend themselves against predators.

pathogen: An organism that causes disease.

pollen: Powdery grains released by the male parts of flowers that can fertilize the female tissue to make a seed. Pollinating insects, such as bees, often pick up pollen that will later be eaten.

predator: (adjective: predatory) A creature that preys on other animals for most or all of its food.

prey: (n.) Animal species eaten by others. (v.) To attack and eat another species.

sea: An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

smoke: Plumes of microscopic particles that float in the air. They can be comprised of anything very small. But the best known types are pollutants created by the incomplete burning of oil, wood and other carbon-based materials.

system: A network of parts that together work to achieve some function. For instance, the blood, vessels and heart are primary components of the human body's circulatory system. Similarly, trains, platforms, tracks, roadway signals and overpasses are among the potential components of a nation's railway system. System can even be applied to the processes or ideas that are part of some method or ordered set of procedures for getting a task done.

tactic: An action or plan of action to accomplish a particular feat.

tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

tract: A particular, well-defined area. It can be a patch of land, such as the area on which a house is located. Or it can be a bit of real estate in the body. For instance, important parts of an animal’s body will include its respiratory tract (lungs and airways), reproductive tract (gonads and hormone systems important to reproduction) and gastro-intestinal tract (the stomach and intestines — or organs responsible for moving food, digesting it, absorbing it and eliminating wastes).

virus: Tiny infectious particles consisting of genetic material (RNA or DNA) surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact many scientists argue that no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

Maria Temming is the assistant editor at Science News for Students. She has bachelor's degrees in physics and English, and a master's in science writing.

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