OMG! What’s on your face? A survey of Demodex skin mites

    

Katherine S. Wydner, Jill E. Callahan, Brandy Garrett Kluthe, and Christina Mortellaro

Advances in Biology Laboratory Education, 2025, Volume 45

https://doi.org/10.37590/able.v45.art58

Abstract

Two species of Demodex face mites are found in humans, D. folliculorum and D. brevis. Dermatologic surveys indicate that everyone has these mites on their skin, but as a normal part of our microbiome they do no harm, except in cases of high infestations, when they may cause skin inflammation. These tiny arachnids, about 0.3 mm long with eight short appendages, have co-evolved with our species. During the day, they live inside hair follicles within our skin and consume sebum from our oil glands. They are fascinating organisms in many ways, having become so dependent on humans that they cannot be cultured in vitro and their genomes are disappearing. There is evidence that these mites vary genetically in different geographic regions of the world. We have developed an inexpensive laboratory activity that will give students the chance to isolate and examine their own Demodex face mites, practice microscope skills, learn about symbiosis, and consider the clinical relevance of face mites. Students will have the option of using different methods for collecting their own face mites, such as gentle scraping of oily areas of skin with a metal laboratory spatula or the edge of a slide. Demodex species slides will also be provided for reference. Students can propose hypotheses and test them based on class results; questions to consider could include whether the number of face mites varies based on the type of face washing performed. Students can also sketch the mites and see if they can determine what stage they are in within their two-week life cycle compared to a reference diagram. Overall, this lab activity will provide a hands-on learning experience that incorporates microbiology, ecology, and evolutionary biology, while also encouraging critical thinking and scientific inquiry among students. Technical skills in microscope use will be achieved through this laboratory activity.

Keywords:  Demodex, Face Mites, Dermatology, Microbiology, Microscopy, Co-evolution

University of Maryland (2024)