Yes, mites live on your face — and they can poop, a new study finds

Yes, mites live on your face — and they can poop, a new study finds

Yes, mites live on your face — and they can poop, a new study finds

If you are arachnophobe, it’s best to stop reading. This isn’t about spiders, but about a different type of arachnid – the microscopic ones that live in the hair follicles on your face. Yes, I’m talking about the mites that naturally live in your pores. No, I’m not lying to you.

Despite what they look like under the microscope, human follicular mites, also known as Demodex, are fairly ubiquitous and usually harmless, if not beneficial. In fact, they are present on almost every human being, usually around the eyelashes and nose, and help keep our pores clean by eating dead skin cells and natural oils. (Someone has to do it.) They only cause skin disease when present in large quantities.

Demodex folliculorum may look like a CGI sci-fi monster under a microscope, but it (probably) won’t hurt you. mikroman6/Moment/Getty Images

From egg to larva to full-grown adult, these eight-legged, semi-transparent creatures only live a few weeks. They spend their lives feeding, mating and laying eggs, all in your hair follicles, from which they only emerge at night.

People have quite an intimate relationship with Demodex. Despite this, scientists know relatively little about these tiny creatures. Now, for the first time, researchers have mapped the genome of the most common species of Demodex in humans. Demodex folliculorum, offer a new window into their microscopic lives — and the evolutionary dead end they may be headed to.

What’s new – In a paper published on Tuesday, June 21 in Molecular biology and evolutionresearchers dug into the DNA of these follicular mites and found a wealth of information about their anatomy, behavior and evolution that scientists had previously only suspected.

“This provides all Demodex researchers around the world with much-needed information about their genetic makeup,” said Benjamin Clanner-Engelshofen, who studies the mite at the LMU clinic at Ludwig Maximilian University in Munich. He was not involved in the recent study, although his research team is also working on the sequence of Demodex’s genome.

The process of extracting the DNA was challenging, especially since the researchers had to clean hundreds of mites by hand using small tools to prepare for the extraction.

“They are so small and fragile,” said Alejandra Perotti, one of the authors of the new study. Other way around. Perotti studies invertebrate biology at the University of Reading in the United Kingdom. “Being so microscopic makes them elusive.”

What they found – The results were rewarding, revealing details of the elusive mites’ lives. For example, scientists knew that the penis of the male Demodex, also called the aedeagus, is in an unusual location: on his back, pointing to his head. The researchers found that a group of genes that determine where and how different body parts develop, called Hox genes, had been shuffled out of their usual order in other animals. This could explain the unique positioning of the Demodex penis, the authors suggest.

And then there’s the anus. Scientists previously believed that Demodex did not have an anal opening and that at the end of their short life they expel their waste products into the follicle. The authors identified the opening under a microscope and found genes that would indicate the presence of an anus — confirming that Demodex can, in fact, defecate before dying.

But it’s the details of the mite’s nocturnal lifestyle that really amazed the researchers. Scientists know that Demodex emerges from its follicular home to reproduce while we sleep. The mite’s inverse scheme can be explained by the hormone melatonin, which helps humans sleep but has the opposite effect on invertebrates like Demodex, stimulating them to move and mate.

To explain this, the researchers looked at the Demodex DNA and found that the mites are missing a few key genes for maintaining a biological clock and producing melatonin. The authors came to a surprising conclusion based on this new information: The mites may be using their human hosts’ melatonin to fuel and fuel their nocturnal mating adventures.

Demodex mites are so small — about a third of a millimeter long — that they can only be seen under a microscope. With their eight stubby legs, they can travel about an inch across your face every hour. Smit et al. Molecular Biology and Evolution (2022)

The big picture – These mites have been part of our body’s ecosystem since before modern humans evolved. Despite their size, they are just as much a member of the animal kingdom as we are. But compared to other arachnids such as ticks, fleas and various types of mites, Demodex are not very complex organisms — they have the lowest number of genes of the fifteen arachnid species the authors examined.

The authors conclude that Demodex loses genes over time and evolves to become less complex by relying more on their hosts. Some of this may be due to isolation and inbreeding, as mite lines mainly encounter other members of the same genetic line and therefore reproduce, which can affect the genome.

All this indicates to the researchers that: D. folliculorum may be headed for an evolutionary dead-end and eventual extinction — though they seem to be doing just fine for now. It’s unclear what effect this capability would have on us, their human hosts.

What’s next – Now that scientists have sequenced the mite’s genome, they may be able to develop better treatments for the skin conditions that can occur when Demodex goes haywire, Clanner-Engelshofen says. These conditions, such as demodicosis and blepharitis, usually affect older adults and people with compromised immune systems and are currently treated with creams such as the infamous ivermectin that kills the mites. This new genetic information could be used to develop better treatments that target and kill the mites’ larvae with little to no adverse effects on the patient, Clanner-Engelshofen says.

And while these results are an exciting first step, they represent the genome of just one mite from one genus. According to Michael Palopoli, an evolutionary biologist at Bowdoin College who has published research on the evolution of Demodex, people in different parts of the world live with different genera of Demodex mites. Genetic sequencing will allow scientists to pull apart the global differences between these mites, he says, and explore how they might affect human health.