D. folliculorum as seen under an electron microscope
(Credit: Power and Syred / SPL)
I.
Like many other people, a friend of mine - let's call her Miss Muffet - has an intense and irrational fear of spiders: If one were ever to crawl on me, I would die, she has said on more than one occasion. And so I've always resisted the urge to inform her about the existence of a genus of skin mites that live on the human face called Demodex ...
II.
Commonly known as face spiders [1], these tiny arachnids are divided into two species; those that live in hair follicles (D. folliculorum) and those that live in the sebaceous glands connected to hair follicles (D. brevis).
Each has a semi-transparent elongated body, covered in scales, and consisting of two fused segments and eight short legs attached to the first body segment. Each also has a little mouth adapted to grinding up dead skin cells and sucking up the oils which accumulate in the hair follicles.
Sleeping by day, at night they like to slowly stroll around the surface of the face in the hope of finding a mate. Once fertilised, eggs are laid inside the hair follicles or sebaceous glands and take 3-4 days to hatch. The larvae develop into adults within a week and then live out their brief lives within the facial pores of their human host.
It's important to note - before you start scrubbing your face like a lunatic - that Demodex pose no threat to our wellbeing; unless they gather in unusually large numbers, in which case they may provoke certain skin conditions that necessitate a visit to the dermatologist.
But that's rare; most people - including my friend Miss Muffet - live blissfully ignorant of the fact that their face is crawling with hundreds - maybe thousands - of microscopic mites, feasting and fucking [2].
Notes
[1] Actually, they don't look much like spiders and the name Demodex - derived from the Greek terms δημός and δήξ - gives us a better idea of their appearance (i.e., fat-bodied and fat-loving little worms). I'm not sure this will do much to calm my friend, however.
[2] Interestingly, whilst Demodex might eat, sleep, and reproduce on your face, they're not shitting on it in a conventional sense as they possess no anuses via which to do so. What happens, rather, is that they retain their waste matter throughout their lives, then, at death, there's one large release of the stuff in what some describe (somewhat exaggeratedly) as an explosion of shit. It's thought that this might cause skin irritation and/or inflammation in some people.
