• When we're sick, our immune system speeds up and produces more mucus — or snot — to kill germs, according to our partner The Conversation.
  • Once germs or other potentially harmful particles are trapped and neutralized, the body gets rid of them by producing so much mucus that one has to blow one's nose, sneeze, or cough to get rid of them.
  • This analysis was conducted by Kristin Ahrens, a pediatric nurse practitioner and assistant instructor in nursing at Purdue University (Indiana, USA).
  • This article was originally written in English and was translated by The Conversation.

When we get sick, it can happen that our nose is runny or congested, this situation that prevents us from breathing properly can be uncomfortable, why does our body react this way?

The answer is quite simple. Producing mucus – or snot – is one of the ways our bodies keep us healthy.

Mucus continuously lines the nose, throat, lungs, and other parts of the body to protect it from bad bacteria, viruses, and other particles. Our bodies continually produce mucus to fight germs and eliminate them.

When we're sick, our immune system speeds up and produces more mucus to kill germs. Although it may sound gross, mucus is very helpful.

A gooey defender

Our bodies create mucus from a mixture of water, protein, and salts. Its sticky texture traps bad microorganisms and other unwanted particles, such as dust or mold, so they can't penetrate deeper into our bodies.

Certain components of mucus prevent bacteria from clumping together and becoming more dangerous. Other elements can even kill invaders who try to make us sick.

And while scientists don't fully understand how, the proteins and genes that cause mucus seem to work together to make it thicker and stickier if necessary.

Once germs or other potentially harmful particles are trapped and neutralized, the body gets rid of them by producing so much mucus that one has to blow one's nose, sneeze, or cough to get rid of them.

When we're sick, our nose sometimes turns red. This is because the immune system, in addition to producing mucus, sends extra white blood cells to the source of the infection.

When they rush to the scene to help fight the infection, the extra white blood cells dilate the blood vessels in the area, making our nose look red. Wiping and blowing your nose can also make it red.

This mucus can have a rainbow of disgusting colors. When white blood cells fight an infection, they release chemicals that can turn it yellow. When more of these cells are needed to fight the infection, the mucus may even turn green.

Usually, after a few days, it becomes clear again and the nasal congestion disappears.

Mucus isn't just found in the nose and lungs.

Our eyes also have a thin layer of mucus that protects them from particles in the air. When we get sick or have an eye infection, the ocular mucus can act in the same way as in our nose, catching and killing germs.

It can also sometimes become thick and yellow. In this case, it is better to call a doctor and not touch your eyes with your fingers at the risk of introducing more germs.

Our stomach and intestines also have protective mucus.

Animals also produce mucus

Humans aren't the only animals that use mucus. For example, dogs and cats have them too.

Parrotfish, wrasses, and other sea creatures produce cocoons of mucus to protect themselves from predators during the night.

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Chameleons use the sticky mucus at the tip of their tongue to attract their prey. Earthworms secrete them to move through the soil.

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This article is produced by The Conversation and hosted by 20 Minutes.

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