Science & Technology

These mites living on your face may go extinct and that's not good news

Demodex keeps skin pores clean

By Rohini Krishnamurthy
Published: Wednesday 22 June 2022
Helpful mites live on our faces but may become extinct! What it means Photo: iStock

Genetic changes in parasitic mites that live and mate on the faces of humans can be disadvantageous for the host, a new study found. 

These organisms, which are 0.3 millimetres in length, likely face a risk of extinction due to inbreeding and loss of genes, findings published in the journal Molecular Biology and Evolution showed.

The study looked at Demodex folliculorum, a tiny parasitic mite found on eyelashes, eyebrows or near the nose. The other known variety of face mite is Demodex brevis, but it was not covered in the study. 

“Demodex folliculorum is the dominant mite species, certainly for Europe. Demodex brevis comes next,” Henk Braig, co-author of the study from Bangor University and the National University of San Juan, told Down To Earth (DTE).

Microscopic image of a Demodex folliculorum mite on the skin. Source: University of Reading

As much as 50-100 per cent adults are estimated to be carrying these mites, according to estimates from other studies.

Despite their prevalence, not much is known about them. For instance, researchers do not understand why they are nocturnal or how they have evolved over the years. 

Braig and his colleagues wanted to bridge this knowledge gap by collecting and analysing the DNA of Demodex folliculorum.

These parasites have adapted to living a sheltered life inside skin pores, Alejandra Perotti, associate professor of invertebrate biology at the University of Reading, who co-led the research, said in a statement.

This has some costs: The researchers recorded changes in the DNA, resulting in unusual body features and behaviours.

The species has become extremely simple, the findings showed. They survive with the minimum supply of proteins — the lowest among related species, the researchers highlighted.

No new genes are being introduced due to inbreeding, they pointed out.

These mites infect new hosts vertically, moving from parent to offspring. This transmission route prevents them from mixing with fellow mites residing on unrelated human hosts. Without them, they lose a chance at acquiring a newer variety of genes, the experts said in their study.

“Demodex is becoming less and less contagious,” Braig said.

Another feature that stood out was a drop in cell numbers. The researchers observed that younger mites have more cells than adults.

This suggests that the mites are evolving from parasites to symbionts, striking a mutually beneficial relationship with their human hosts, the report noted.

Braig said:

They are parasites only for a very few people and, in at least one case, because of a mutation in the human genome of these people. In many cases where people have problems with Demodex, it is a consequence of other problems, not the cause.

“Demodex has a beneficial function in humans: Keeping the pores clear,” the expert added. These organisms feed on sebum, an oily, waxy substance produced by the human body, according to researchers.

Further, these organisms are losing some of the genes that produce repair enzymes. “If this continues, the genome will degrade more and more,” Braig said. This puts them at risk of potential extinction, the expert added.

Loss of genes can also explain why the mites stay active at night. Genes that keep them up during the day have disappeared, according to the findings.

A change in gene arrangement has given rise to strange mating behaviour, the study noted.

The penis of males protrudes upwards from the front of the body, the researchers said. This arrangement suggests that they must position themselves beneath the female when mating, they explained.

A 2015 analysis suggested that Demodex folliculorum could shed light on ancient human migrations. Some mites, according to the study, are better equipped to survive and reproduce on hosts from certain geographic regions. 

The researchers hope to calculate the number of mites residing on the human body and estimate the population size.

Subscribe to Daily Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.