Battling demodex on the lid margin is a regular occurrence for most ODs. Demodex, more commonly referred to as mites, are small arthropods belonging to the subclass Acari.
Mites exist in an array of habitats and live as parasites on plants and animals. Approximately 48,000 species of mites have been described.1 In almost every adult human, Demodex folliculorum or Demodex brevis inhabit the eyelash, other hair follicles, and sebaceous glands.
Other mite species, specific to each mammal, are similarly harbored by their host species. Mites are not found on the skin of newborns. Hair follicles are thought to become colonized by mites during childhood and early life by transmission from adults, similar to the process of acquiring other microbes (microbes include bacteria, protozoa, fungi, algae, amoebas, and slime molds). Microbe acquisition is a lifelong activity that begins the moment we are born.
Previously from Dr. Mastrota:Using precision medicine for dry eye
Humans need microbes
Though babies develop in a sterile environment, a newborn emerges as a bacterial sponge picking up microbes that contribute to its health.
Microbes can be found in their greatest concentrations in the ears, nose, mouth, vagina, digestive tract, anus, and skin.2 Like microbes, demodex mites are a natural part of the human microbiome and may serve a useful function.
It is important to consider humans are not biologically self-sufficient—they must host microbes to avoid disease. For example, genes carried by bacteria in the gastro-intestinal tract allow humans to digest foods and absorb nutrients that otherwise would be unavailable.3
These fundamental microbes produce beneficial compounds, like certain vitamins and protective anti-inflammatories that humans cannot produce by themselves. For example, members of the gut microbiota can produce anti-inflammatory factors by enhancing cellular immune responses as well as generate Vitamins K and B.4
Related: What’s all the craze about demodex?
Symbiotic relationship important
Humans and demodex may have a symbiotic relationship. There are several classes of symbiosis:
• Commensalism: one organism benefits, and the other is neither harmed nor helped
• Mutualism: both organisms benefit
• Obligate scenarios: both symbionts depend on each other for survival