Mites, invisible to the naked eye, are eight-legged arthropods closely related to ticks and spiders. Almost all humans actually host these creatures on their faces. There are two species that make the human face their home: Demodex folliculorum and Demodex brevis. The former spends its time in pores and hair follicles, while the latter settles deeper, in the oily sebaceous glands.
(photo credit: EYE-OF-SCIENCE_SPL)
Scientists do not know much about these mites, and it wasn’t until 2014 that researchers at North Carolina State University in Raleigh found visible mites on 14% of people they studied and Demodex DNA on every face they tested. It is not clear how many we have on our faces, but it is likely that it varies in the range of hundreds to thousands. We may have up to two mites per eyelash. There is also evidence that the number of mites varies from person to person, depending on age and other factors. As we get older, we accumulate mites. But we get them at a very young age; mothers may give them to their children through birth or through contact with mammary tissue, where they have been found to live.
Nobody knows for sure why mites live on out faces. It is unclear what they eat, but there are some theories. Some believe that they consume dead skin cells, and others believe that they eat the oil from the sebaceous gland. Others believe that they feed on the bacteria on skin. Surprisingly, these mites are probably not harmful to most of us. It appears that they are not parasites, which cause harm to the host; instead, they may have a commensal relationship with humans: they gain something from us but do not cause harm by doing so. The only known skin condition they cause is a disorder called rosacea, which can cause permanent redness, spots, and burning and stinging sensations on the face. The number of mites on people with the condition tends to be much higher than normal. Even then, it is doubtful that the mites actually cause the problem.
Mites are creatures that do not have anuses. This means that they cannot push waste out of their bodies. Because of this, they save up everything until they die. They have been said to ‘explode’ at the end of their lives, but this is a bit of an exaggeration. In reality, it’s more like a large flush of bacteria that then degrades on your face. Thankfully, there has been no evidence of harm associated with this process.
These creatures have been living on our faces for a long time. Some speculate that we first got them from canines, which have similar mites living on their faces. Different areas of the world have distinct mites. This may reveal how our ancestors migrated the planet, telling us about how modern populations evolved. It could also tell us how we evolved, and if our immune systems have changed as a result, or how we respond to disease.
Mites are only one example of an organism living inside of our bodies. In reality, microorganisms compose over ninety percent of our cells. Our bodies are thriving ecosystems to microbial life. (Natalie Gilmore)
For more info:
This lab is studying face mites: Rob Dunn Lab