The face of the adult human is covered in microscopic eight-legged creatures, not an appealing image, but it could help trace our path across the planet.

Face mites are just half a millimetre long, semi-transparent, have eight legs and look somewhat like a see-through caterpillar, though they are invisible to the naked eye.

Until recently, scientists thought that only a small portion of the population had face mites, but a new study from the US found 100 per cent of the 253 people over age 18 sampled had mite traces on their faces, suggesting that the mites could be universal inhabitants of adult humans.

The study also found that human faces are home to two different species of the mites.

One is called Demodex brevis and lives in sweat glands, while the other, Demodex folliculorum, lives in the hair follicles of eyelashes, eyebrows and facial skin.

It appears that the mites collected from faces in different parts of the world can be genetically distinguished from one another, which makes them useful for tracing human populations and migration patterns.

The report has been published in PLOS one, and is accessible here.