What is Mucus?

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  • Written By: M.C. Huguelet
  • Edited By: Heather Bailey
  • Last Modified Date: 28 May 2019
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Mucus is a slick substance secreted by the mucous membranes that line many of the body’s inner surfaces, such as the lungs and the nasal passages. It consists of proteins, antimicrobial enzymes, antibodies, and salt. While the average person produces around 4.25 cups (approximately 1 liter) of the secretion each day, it is normally fairly thin and unnoticeable. It is usually only when the body becomes infected that it takes on the nostril-plugging, cough-rousing consistency that sends many running to a healthcare professional for relief.

This substance has three primary functions: keeping bodily tissues moist, trapping foreign bodies to prevent infection, and attacking the causes of existing infections. Its moisturizing properties are important to the health and comfort of the body’s many mucous membranes. Once secreted, it forms a kind of shield of dampness over these surfaces, without which the membranes would quickly become dried out and irritated.

While the stickiness of mucus may be disagreeable, it is this very property that allows the substance to perform an important protective duty. It traps foreign bodies like bacteria in its gooey clutches before they can set up shop in the body and cause an infection. Once these bodies have been trapped, they are eliminated by the antimicrobial enzymes contained within the substance.


Despite the body’s best efforts to nip infection in the bud, sometimes viruses and bacteria manage to invade and cause illness. When this happens, the mucus plays yet another role. Its antibodies seek out the infecting bodies and then kill them.

It is when the body has been infected that the mucus takes on the qualities with which it is generally associated: green color, thick consistency, and seemingly endless abundance. This green hue is caused by a green enzyme contained in the antibodies. When the body is infected, these antibodies are dispatched to in larger quantities than usual, giving the substance a noticeable coloration.

Thickness and increased production are also defensive features that enhance the material's ability to trap and neutralize infection. While in the throes of a drippy cold or stuffy sinus infection, it can be tempting to sideline respiratory secretions with a decongestant or antihistamine. Before cursing the sticky stuff, however, patients should remember that it plays an important role in making — and keeping — the body healthy.


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Post 7

@healthy4life – Since you've already had it for two weeks, you should start feeling better soon. The most intense part of bronchitis lasts about two weeks, but you will probably be dealing with the cough for longer than that.

It took me a month to feel a lot better when I had bronchitis. The cough became much less severe, but I do have some bad news for you. Some of the mucus can linger for a long time, and you may find yourself coughing it up every morning for years to come.

It's been a couple of years since I had bronchitis, and I still wake up every morning coughing up mucus for the first hour or so. It isn't nearly as intense as when I was sick, but it's definitely noticeable.

Then again, this doesn't happen to everyone. You may be feeling 100% better in the next few weeks.

Post 6

I've been dealing with bronchitis for two weeks now, and I still have mucus in my lungs. Since it was caused by a virus, the doctor said there's nothing I can take to make it go away.

I feel like I'll never be rid of this mucus! Every few seconds, I will launch into a coughing fit brought on by nothing other than breathing. I cough until my sides ache, and even though some of the mucus comes up, there is an endless supply of it stored in my lungs.

How long will I have to deal with this? Can anyone tell me how long it takes for bronchitis to go away?

Post 5

Did you know that you sometimes have mucus in your poop? I was surprised to learn this, but it's fairly normal, because your intestines are lubricated with mucus to help your poop move along. You might even see it floating in the toilet sometimes.

Post 4

@write79 – You may be right about that. However, nasal mucus during a cold is just so intense that I feel like I have to find a way to slow it down!

Last time I had a bad cold, I got so tired of wiping my nose every few seconds that I actually shoved a tissue up my nostrils. In just fifteen minutes, it had become completely saturated with mucus!

I took antihistamines and decongestants, but even they couldn't stop the mucus. Maybe that's why it took me so long to get over the cold.

Post 3

For Post 2, reactions to allergies are an over exaggeration of the body's immune system to a certain substance, mold for example, and although it may not be a threat to the body, the body could take it as one and may produce more mucus as a response.

Post 2

Is there a reason why mucus is increased when you are suffering from nothing but allergies? There is no infection for the body to be fighting off, so why is mucus a problem?

And is the fact that there is no infection present the reason why clear mucus is a sign that allergies are the problem and not an infection?

Post 1

Wow, I had no idea that mucus was such a helpful thing. I don't know if mucus is the reason, but I always feel like I get rid of a cold better if I don't take decongestants.

I've noticed that when I take the medicine, it almost feels like instead of the cough, mucus, and stuffiness being gone, it's just trapped. Maybe these medicines aren't letting the mucus do it's job!

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