They’ve got eight legs, feast on dead skin cells – and are living on your face right now.

Thousands of mites are crawling, eating, sleeping and have sex on your skin, but they can only be seen through a powerful microscope.

But, before you rush out to buy an extra-strong face wash, it’s worth noting that these creepy crawlies aren’t a serious problem and are almost entirely harmless.

There are two species of mite that live on your face: demodex folliculorum and demodex brevis, BBC Earth reports.

Demodex folliculorum are commonly found around human hair follicles, usually in greater numbers around the cheeks, nose, eyebrows, eyelashes and forehead.

They can also be found in other parts of the body such as the arms, chest, and ears, but they do not invade internal organs.

We aren’t born with these mites – they are picked up through contact with other people, as well as from things such as towels and pillow cases.

Under normal conditions, they are not harmful and are classed as commensals (the mite benefits from living on people but there is no harm or benefit to us).

Mites and humans have had a long relationship together seeing as human earwax from 1842 contained the tiny critters.

During the day mites feed on dead skin cells within hair follicles, while at night they emerge to mate and lay eggs.

Heavy infestations of mites can arrive in adolescence – thanks to the sebaceous glands during puberty – and can last up to middle age.

The distribution of mites varies person to person, but men are likely to have heavier infestations because they have more sebaceous glands.

A study published in the journal PLoS ONE in 2014 found that, in a small sample of 29 people, 100% of subjects older than 18 had mite DNA on their face (for 18-year-olds, the number dropped to 70%).

“It’s hard to speculate or quantify but a low population would be maybe in the hundreds,” study researcher Megan Thoemmes, of North Carolina State University, told BBC Earth.

“A high mite population would be thousands.”

Demodex brevis are very similar to demodex folliculorum but they survive in sebaceous glands adjacent to hair follicles, for example, around the eye area.

During a severe infestation, people may experience adverse effects such as rough, dry, and itchy skin.

There are therapies that kill demodex mites but you can’t get rid of them forever as they rebound every six weeks.