Not all bugs in your skin need to be a nuisance

Plagues of small bugs on and in the skin alternate. Mosquitoes and/or wasps. Lice, fleas, ticks, oak processionary caterpillars, all kinds of worms, bed bugs in tourist hotels.

Now it is the scabies mite that – much more often than in years before – attacks our skin. And receives media attention, with horror stories, about corridors that the mite digs into human skin, causing unbearable itching.

Adolescents and young adults in particular are victims. They easily infect each other. Especially during the corona period, when group lounging at home was a forced craze among young people. That is probably the explanation. Mites thrive in those conditions.

All those bugs on the skin can cause red spots, skin swelling, itching and even (serious) illness. What is special is that not every resident of the skin causes a nuisance. The best example is also a mite – the demodex mite. Hardly anyone knows about it, but demodex mites live in the skin of almost all inhabitants of the Netherlands and other countries at moderate latitudes. They do not burrow into the skin like the mange mite. They live in existing skin cavities.

There are two types: Demodex follicularis lives in hair follicles, Demodex brevis lives in sebaceous glands. They prefer the scalp. The follicularis variant is fully adapted to human hair follicles. It is longer than the convex mange mite and fits nicely in hair follicles.

It has been known for a year that this mite is genetically completely dependent on humans. Due to accidental gene mutations, over thousands of successive generations, the animal has lost many genes. He can do without those, because he lives safely in those hair follicles. There is enough food and he doesn’t have to move much. For example, it has fewer muscles than other mite species. Substances that are of vital importance to him, and that he can pick up from his host, he no longer makes himself. No demodex mite without humans.

The mite in hair follicles almost never causes problems. Sometimes people with falling eyelashes, or people with burning, dry eyes, find that too many mites live in hair follicles and eyelash glands.

Are those permanent skin inhabitants good for us? One species eats dander. Perhaps they clean hair follicles so that healthy hairs continue to grow from them. We do not know. The other species eat sebum. Do we therefore suffer less from clogged sebaceous glands, from acne? Unknown. Critters that hardly cause a nuisance receive little attention from researchers.

We know a little more about parasites, such as the scabies mite. Humanity and its evolutionary precursors are eternally engaged in a life-and-death struggle with their assailants – from the smallest pathogenic viruses and bacteria, right through to the larger parasites, such as mites, ticks and worms.

That battle gave us a complicated immune system, in which hundreds of complex genes are active. There are researchers who think that immune diseases, such as asthma and chronic intestinal inflammation, are more common now that children experience fewer worm infections.

Any benefit of the mange mite to humans has never been established. In healthy people, the immune system succeeds in getting rid of the scabies mite. But no one knows whether this will also be good for beleaguered humanity in the longer term.

If we get the chance to eradicate the scabies mite, will we do it? Or is man obliged to maintain all animal species, even if they only live in man? Is this in the interest of biodiversity on earth?

The practical answer is that there are more important health issues to spend our money and time on for now.

Read also: First aid for scabies: 21 questions and answers