Human parasites of genus Demodex
"...don’t bother scrubbing your eyes out tonight when you shower. Almost nothing gets them out." - Tribe.net¹
There are few cute parasites, and true to form, these are ugly little blighters. Practically legless, pale wrigglers, they do indeed live, head-down, in the follicles of your eyelashes.
They are not insects, rather a type of arachnid similar to ticks. There are two species that inhabit you. D. folliculorum and D. brevis are both tiny creatures, around one-hundredth of an inch (a third of a millimeter) in length. Follicularum, as its name suggests, lives in the hair follicles of your eyelashes and eyebrows, whilst brevis lives in the sebaceous glands on your face. And yes, you have them. Even as you read this, they are face-deep in dead skin cells and sebum, gorging themselves on your facial wastes.
Okay, having possibly put you off your next meal, let me reassure you about a few things. Firstly, they appear not to poop. They are highly efficient at what they do, and use everything they eat. Secondly, they will not run around your face as you go about your daily affairs - they do not like the light, so bury themselves in your face during daylight hours. If you could see them now, all you would see is eyelash mite rump, about a fifth of the thickness of the eyelash.
So, I hear you ask, what happens in the dread dark? Well, that is when they come out. They can move, albeit quite slowly; if you slept for eight full hours, it is unlikely that they'd walk from eyebrow to chin. But move they do, and for one very good reason. They need to mate. Yes, they have creepy sex on your face, then return to lay a dozen or so eggs, to found a whole new generation of mites. They can live for several weeks, and when they die, they decompose, to be recycled as even more mites.
For all that disgusting behaviour, they do far more good than harm, cleaning up the facial gunge and detritis that is an inevitable part of life. As I mentioned, they don't poo on your face and will never embarrass you by running down your nose during a dinner date. Just once in a while they may cause blepharitis (inflammation of the eyelid) or if the population is extremely high, a condition known as demodicosis, an inflammation of the skin.
They tend to be more common on older people, possibly because they produce more facial oils, but it is true that the majority of folk will have at least a few. So, you want to see them? Tweak out an eyelash, pop it under the microscope and either marvel, or be disgusted. But do embrace your mites, because they are with you for life.