Dust mites are tiny organisms that live in piles of dust, and feed on human skin flakes. You may not have realized it, but your face is covered in microscopic organisms as well.
Demodex mites are a species of arachnids that live on our skin, and the skin of other mammals. They are microscopic, too small to be seen by the naked eye. Scientists have found these mites on the skin of all mammals they have tested for, except for egg-laying mammals like the platypus.
A group of scientists just published an article about these mites in the journal PLOS ONE on August 27, titled "Ubiquity and Diversity of Human-Associated Demodex Mites."
The abstract of the study called these mites "the animals with which we have the most intimate interactions." However, we do not know very much about these mites still. We haven't fully looked at these mites before and there was a lot to be discovered about these organisms. Before this study, most mammals had not been tested for the mites, nor had many populations of people.
When post-mortem testing was performed, all humans studied over the age of 18 had at least one species of Demodex on their body. However, when the tests were done on living people, the researchers only found mites on 55 percent of participants. This suggests that likely all humans have mites, but the method of testing they are using (testing in patches) may be inadequate. The researchers expect to find more species as they look at more people from diverse geographic areas.
Less than 10 percent of the cells on our body are actually part of us. The rest are different organisms, like fungi, intestinal worms, and bacteria. One of the mites the study looked at, D. folliculorum, lives on hair follicles in your body. The average person has about 5 million hair follicles on their body, which gives these mites quite a lot of room.
The other main species the study focused on, D. brevis, mostly lives above follicles of vellus hairs, short fine hairs that are mostly found in children and women.
The study used participants who volunteered to have their faces scraped for mites. The scientists did not need to use a microscope to test for mites: they were able to detect their presence by testing for mite DNA from human skin samples. You can see pictures of the mites that the scientists found online here.