Snot is easy to laugh at, but it is also a body defense. Snot is mucus, a sticky, slimy stuff that the nose makes. As of November 2026, experts say the nose and sinuses make about a quart (about 1 liter) a day, but they also say nobody knows the exact amount. That is a lot of stuff to make without a count.

What is it made of? Water, mucin proteins, defense proteins and salt. Cells in the mouth, throat, nose and sinuses make it. It lines the inside of the nose, and it also lines the lungs and the digestive tract. The clear, thin kind is normal and healthy, and everybody makes it, so there is nothing to be shy about.

Think of it as a trap. The air we breathe has dust in it, and sometimes viruses and bacteria float in the air too. The nose traps many of them. Hairs inside the nostrils help block bigger bits of dirt, and mucus-covered hairs help trap larger particles as they enter. All the while, it keeps the inside of the nose moist.

So it keeps moving, all day long and all night too. Tiny hair-like strands called cilia wave back and forth all the time. They line the airways and push mucus along, like an escalator. They sweep it, with the stuff it has caught, toward the throat, where the ride comes to an end. It never stops.

Mucus drips down the back of the throat, carrying the dust and germs it caught. Then we swallow it. In the stomach, it meets acid, which helps destroy the harmful material. In the lungs, mucus acts like a shield against germs, and the dust stays out too. It is a clean way for the body to get the job done.

A booger is dried mucus mixed with bits of dust, pollen and dirt. Blowing your nose into a tissue is a good way to clear out boogers, and a tissue traps germs. Picking the nose can make it bleed, and boogers contain lots of germs, so a tissue is a better tool for the job than a finger.

Some days the nose runs more than it should, or it gets blocked. That is a main sign of a cold. A cold usually gets better on its own in about one to two weeks. Does the color of snot tell the story? The color of snot alone does not tell you what is going on inside the body.

Colds are spread by germs from coughs and sneezes, which can land on hands and surfaces. That is why hands matter. Washing hands with soap for about 20 seconds is a good length. Washing helps stop colds from spreading, and it helps you stay healthy, so it is a good habit to keep.

Words to know

• mucus: nose slime
• mucin: mucus protein
• cilia: tiny hairs
• escalator: moving stairs
• defense: protection

The short version

Snot is mucus, a sticky, slimy stuff made by cells in the nose, mouth, throat and sinuses. It is water, mucin proteins, defense proteins and salt. It catches dust and germs so they stay out of the lungs, and cilia push it along like an escalator.

Quick facts

• Snot is mucus, a sticky, slimy stuff that the nose makes.
• Mucus is made of water, mucin proteins, defense proteins and salt.
• As of November 2026, the nose and sinuses make about a quart (about 1 liter) of mucus a day, but experts say nobody knows the exact amount.
• A booger is dried mucus mixed with bits of dust, pollen and dirt.
• The color of snot alone does not tell you what is going on inside the body.