Why is snot sticky?

Most of the time, you probably barely notice the mucus in your nose. But when you have a cold or seasonal allergies, the glue-like goo that floods your nostrils suddenly makes breathing laborious and consumes your thoughts.

But have you ever wondered why snot is so remarkably sticky?

Mucus may be annoying when it's clogging your nose, but its stickiness serves an important purpose: It helps trap and remove tiny irritants that get sucked into your nasal passages along with inhaled air.

Without mucus, dirt particles and harmful microbes would reach lower parts of the respiratory tract and damage the delicate tissues in the lungs, Dr. Johannes Uys, a primary care physician at Broadgate General Practice, a clinic in London, told Live Science by email. Therefore, the consistency of nasal mucus plays an important role in your immune defenses, he said.

Related: What does it look like when your sinuses are clogged?

That said, snot is more than a physical barrier to airborne pollutants; it also contains antiviral and antibacterial components, including antibodies, proteins produced by the immune system to help prevent infections. Snot also contains lysosomes, specialized cell units containing enzymes that break down invading pathogens, according to the medical resource StatPearls.

The consistency of your snot can tell you a lot about your health, when you couple that information with other symptoms, Dr. Jay Lee, a member of the board of directors of the American Academy of Family Physicians, told Live Science by email.

"While normal mucus is clear and watery, cloudy or discolored mucus ― like green or yellow ― could signal that you have a viral or bacterial infection," he said. That's because snot contains dead white blood cells, a type of immune cell, and other waste products left over from an immune response. So during an infection, it changes color.

"You may also notice a lot of congestion, because infections can lead to inflammation in the [mucous] membranes that line the nasal airway, causing airway glands to produce more mucus," Lee said. The mucus not only increases in volume, but it also gets thicker ― again, that is due to an accumulation of dead microbes and cells that arrived to fight the infection.

To a large extent, snot owes its stickiness and gel-forming properties to molecules known as mucins, Lee said.

The structure of these sticky molecules resembles bottlebrushes: They have a thin, elongated protein backbone with thick, bristly carbohydrate branches sticking out of it. This unique shape allows mucins to bind with each other in a network that can resist changing shape. For this reason, mucus in your nose can rapidly snap back to its initial shape even if its structure is briefly disrupted when you cough or blow your nose, according to a 2018 review published in the journal Annual Review of Cell and Developmental Biology.

The chemical structure of mucins also gives them the ability to bind significant amounts of water, which is what contributes to the thick, gelatinous texture of snot, Uys noted.

Mucins are a scaffolding for other active components in the mucus, but they do much more than that. For example, these sticky molecules can interact with the microbes that naturally reside inside the mucous barrier, serving as a source of fuel. While supporting the growth of some bacteria, mucins can also help prevent harmful microbes, such as the bacterium Staphylococcus aureus or the yeast Candida albicans, from adhering to the walls of your nose, the Annual Review authors noted.

So, next time you're struck with a stuffy nose, remember the silver lining: Your snot is helping you fight off the infection.

This article is for informational purposes only and is not meant to offer medical advice.

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