What are snot and what do they do?

Everyone knows snot, but not many know what they really are and what their function is. Although it seems incredible, an average adult produces about a liter of this substance by the nose and one more liter down the throat every day.

Snot has different textures and colors. There are soft and hard, black and white, green and yellow. In general, they are related to dirt, but their main function has to do with preventing many undesirable particles from entering the respiratory system.

One way or another, the snot indicate whether a nose is working as it should or not. Although the habit of picking the nostrils to extract that sticky substance is very widespread, it is best to clean with a tissue.

What is nasal mucus?

Mucus is spoken of to refer to the fluid that comes out of the nose. This is not the only mucous secretion that the body produces, but that name has become popular. Bronchial secretions are often called phlegm or expectoration.

Thus, mucus is a viscous fluid secreted by the epithelial cells of the nose and other organs. These cells have cilia, which are a kind of hair. These move mucus into the nostrils.

They fulfill several functions and the most important are the following:

  • They act as lubricants: They help keep the nose and sinuses moist. This protects from irritation caused by rubbing against an object or particle.
  • They are a protective shield: the tissue of the nasal passages and sinuses is quite fine and delicate. Snot helps protect it.
  • They form a barrier: They help trap and expel foreign particles that enter the nose, such as dust, pollen, bacteria, and viruses.

In this way, the function of mucus can be synthesized by saying that it is a defense and protection mechanism against external agents that can enter the body through the nose. They are key to fighting allergies and colds.

Sinusitis is the accumulation of mucus in the paranasal sinuses with inflammation of the mucosa that lines these cavities.

Keep reading: Sinusitis in children: symptoms, causes and treatment

How is mucus formed?

Snot is produced inside the nose and, in principle, they are a substance that contains water, proteins, some chemicals and salt. They have a viscous and sticky texture, which allows them to trap harmful substances from the environment.

Most of the mucus produced by the nose and throat is mixed with saliva and swallowed. Part of it stays on the nose. When a person sneezes or blows his nose, the mucus is expelled. If not, it stays in the nose and dries up.

If a person catches a cold, the body produces more histamine. This is a substance that causes the membranes of the nose to swell and produce more mucus. This forms a thick layer of mucus that reinforces the protection of the nasal tissue.

Likewise, when there is more mucus it should be expelled more frequentlyEither because people blow their noses more regularly or because they sneeze more. This helps to expel the infectious agent. Something similar happens with allergies.

What is not mucus?

There are many popular myths surrounding snot. As myths that they are, they do not correspond to the truth. It is said, for example, that they are brain cells that descend from the skull and reach the nose, which is false.

In the same way, some claim that it is traces of cerebrospinal fluid. It is also said that green snot implies a serious infection or that not having it in the nose means being cleaner. None of that has any foundation.

Also read: Mucophagia: is eating snot a dangerous habit?

Why does mucus change color?

One of the most striking aspects of snot is that they change color. Generally speaking, this occurs because of the substances that come into contact with them. From that point of view we can find different shades.


It is the usual tone and the one that is considered normal. However, if they leak too much, it may be a sign of a cold or allergic rhinitis. So the absence of color is not always a sign that there is no health problem.

Yellowish or greenish

Yellow or greenish mucus is a sign of an infection, which does not have to be serious. They take on that tonality because the immune system increases the production of defense cells called neutrophils.

Such cells secrete enzymes to kill the infectious agent. One of those enzymes, peroxidase, gives mucus that tone. The usual thing is that the mucus changes color gradually: it goes from transparent to yellow and then to green.

Red or brown

This color means there is a blood component in the mucus. It is possible that some of the small blood vessels that are in the membrane of the nose have broken or that a small injury has been caused by sneezing or blowing too much. This tone should not immediately alarm you.

Repeated blowing of the nose can damage the mucous membranes, adding blood to the mucus.


It is not very common for snot to have this color. The usual is that if they acquire that tone it is because smoke or soot has been inhaled. It can also be a sign that you have breathed in a highly polluted atmosphere.

Snot is a natural thing

Snot can be repulsive, but it's actually a sign that everything is working fine in the nose. Even so, it is best to teach children not to eat them. Not that they are toxic, but in any case they are a residue of the body.

It is also important that neither children nor adults pick their noses, as they can easily injure tissues. It is best to blow gently or use a nasal rinse to cleanse yourself.