across your face right now. Yes, you,

and at some point, maybe now, maybe in a few days,

it's going to find a nice cozy pore in your skin

and lay a single enormous egg.

Meet the face mites. They're smaller than a grain

of sand, are a kind of arachnid like spiders,

and they feast on the oil and cells in your skin,

particularly on your oily nose, cheeks, and forehead.

Scientists suspect they've been living on us

since the dawn of humanity over 200,000 years ago,

and today, studies suggest practically every adult

on the planet has thousands of them.

Odds are you've been living with them your whole life.

Babies quickly get them from their parents

a few days after birth, and once those face mites

are on you, the only thing they enjoy as much

as slurping oil and nutrients from your pores is

having sex all over your face.

Afterwards, females burrow deep

into your pores where they lay their eggs.

The eggs end up in one of two places

depending on the species of face mite.

The first species, called Demodex folliculorum,

lays its eggs in your hair follicle,

while the second prefers nesting in your sebaceous glands.

And in under two weeks, the babies hatch,

mate, lay their own eggs and die,

leaving behind a pile of decomposing corpses.

Now, you can wash some of this off,

but you'll never eradicate them completely

because even if you treat them with antibiotics,

they'll return in about six weeks, tops.

You'll pick them up from towels, pillows,

and your loved ones.

Well, that all sounds horrific,

but usually face mites are harmless.

They only become a problem when they multiply

out of control. This can happen in people

with an impaired immune system.

It's also been seen in people with a painful skin

condition called rosacea.

Normally, you'll have around one or two mites

per square centimeter of skin,

but one study found that people with rosacea

had 10 times the normal amount.

Believe it or not, in some cases,

face mites can be useful.

Researchers can actually study your face mites

to learn about your ancestors.

You see, most mites often stay within a community.

So over time, they've evolved into distinct lineages

in different geographic regions, and by comparing

their DNA, scientists can trace how different groups

of humans migrated across the world.

For example, a study found that European mites

genetically diverged from East Asian mites

around 40,000 years ago.

That's the same time European and East Asian humans

parted ways. Pretty handy.

So when it comes down to bugs crawling all over you,

it could be a lot worse.