It’s not a sexy topic (unless perhaps you have a fetish), but it is a useful topic to know about.

So, let’s get down to business with this much-maligned bodily fluid:

What is mucus? And why?

Sometimes, it can seem that mucus only exists to be an inconvenience, and to convey disease.

And… Actually, that’s mostly true.

While some kinds of mucus have other jobs beyond the scope of today’s article (did you know semen is mostly mucus? If not, now you do), the primary job of most of our mucus is to stop things (especially pathogens) going where they shouldn’t.

So, in essence, it really does exist to be an inconvenience—to pathogens. And to convey those pathogens to where they can be disposed of safely, either outside of the body, or to be an easy meal (what with being stuck in mucus, and thus at least moderately immobilized) for our various active immune cells. To make matters worse for the pathogens, there are (usually) enzymes in our mucus that have antimicrobial properties, too.

Some of mucus’s protective role can be in other ways too, such as by lining our stomach. You know, the stomach that contains the acid that can dissolve meat, despite us also being made of meat.

The slimiest rainbow

Ok, maybe not the slimiest rainbow—there’s probably a YouTube slime channel producing more colors. But, our noses are capable of dispensing astonishing quantities of mucus sometimes, and the color can vary widely, so here’s what we can know from that:

Clear

This is as it should be, in good health. If you’re getting lots of it but it’s clear, then it’s usually allergies, but watch out in case it changes color, heralding an infection. This “clear is how it looks when in ideal health”, by the way, is why when someone is sobbing in abject grief, any mucus that shows up to add to that picture will generally be clear.

White

As above, but now inflamed. Inflammation is usually something we don’t want, but in the case of a threat from a pathogen, we actually do want acute inflammation like this—the body is assembling its armies, of which, the most visible (when they appear in mass) are white blood cells. Because of their abundant presence at this stage, the mucus will also become thicker.

Yellow

As above, but the battle is now truly underway, and the yellow color comes from dead white blood cells. This does not, however, mean the battle is necessarily going badly—the body treats its white blood cells as very disposable fighters, and their deaths in large numbers are expected and normal when doing battle.

Green

As above, but neutrophils (a specific kind of white blood cell) have joined the party. They release an enzyme that colors the mucus green—and kills a lot of pathogens. Popular lore says that green mucus means a bacterial infection, but it’s not always so; these can be deployed against viruses too, depending on various factors beyond the scope of this article (but generally pertaining to severity). In any case, this too does not mean the battle is necessarily going badly, but it does express that your body is taking it very seriously—and you should, too.

Red

Nothing to do with infections, usually—it’s just a little blood (the red kind, this time). Usually it got into the mucus because the mucus membrane got damaged, usually due to some kind of physical trauma (e.g. very vigorous nose-blowing, poking things up the nose, etc) or sometimes if the air is very dry (then the mucus itself can dry out, and become stabby inside the nose; when more mucus is produced, it gets infused with blood from the injury).

Pink

As above, but combined with the “white” stage of infection response.

Orange

As above, but combined with the “yellow” stage of infection response.

Brown

As above, but the blood has oxidized—or, as a completely alterative possibility, it could mean you have been breathing a lot of pollutants. Smoke of various kinds (from fires, from smoking, etc) can cause this.

Black

There are various possible explanations here and all of them are bad. Get thee to a doctor. Superficial examples include:

• Fungal infection (you thought toxic black mold was bad when it was on the wall of the house, wait until it’s on the walls of your respiratory system)
• Blood, in abundance, oxidized (which begs the question of what caused that, but certainly: something wrong is not right)
• Pollutants again, but this time at absurd levels of exposure

That last one might sound very transient and self-correcting, but it’s not, and it comes with many increased short- and long-term health risks.

Want to know more?

Knowledge is power, so read up, and stay well:

• Beyond Supplements: The Real Immune-Boosters!
• The Cold Truth About Respiratory Infections
• Why Some People Get Sick More (And How To Not Be One Of Them)

Take care!