Demodex Spp. – Face Mites
Follicle Mites are Common Parasites of Human Facial Skin
Demodex folliculorum and Demodex brevis live in hair follicles and sebaceous glands and usually do no harm. Many of us have these tiny skin parasites.
Mites are small creatures visually similar to insects but with four pairs of legs instead of three. Many mites are parasites of animals and plants: Demodex folliculorum and Demodex brevis are parasites of humans. These two microscopic mite species live on the face, tucked into the hair follicles. They are referred to as demodex mites, follicle mites, or face mites.
Where do face mites live?
A hair follicle is a long narrow tube leading down from the skin surface to the root of the hair. Branching off the side of the hair follicle quite near the surface is a sebaceous gland that continually produces sebum, a fatty secretion to moisturize and protect the skin. While hair follicles and sebaceous glands occur virtually all over the body, follicle mites seem to have a predilection for the follicles and glands of the face. Early research indicted that they are most numerous around the nose and eyes, but some recent studies have found the highest numbers on the cheeks and forehead.
Follicle mites are long and thin—the better to fit inside a long thin hair follicle—with their four pairs of legs right up at the head end and the rest of their tubular body dragging behind. Demodex brevis mites live in the sebaceous glands while D. folliculorum mites occupy the hair follicles—both species feed on sebaceous secretions and dead skin cells, both reproduce in the follicle or gland, and both occasionally leave the follicle and travel across the skin to a new follicle.
Who has face mites?
Demodex mites are very common in humans. The older you are, the more likely you are to have a few mites living in your follicles, with some sources stating that virtually all senior citizens have them. Follicle mites are passed directly person to person through skin contact or on shared towels and other fabrics.
Because they are microscopic, you generally don’t know that you have follicle mites. To confirm that they are present, you would need to gently scrape oily skin secretions off the surface of the skin or attempt to express some sebum from the hair follicles on the face. The material could then be examined under a microscope; however, if no mites are seen, they might simply be too few and too deeply lodged in the hair follicles to be detected in this manner. For most of us, however, the presence or absence of follicle mites on our faces is of little consequence.
Do face mites cause skin problems?
For years, follicle mites were thought to be commensals—parasites that lived on us without doing any harm. Certainly, the majority of people who have them never know that they are there and suffer no adverse effects from them. Demodex folliculorum, however, can multiply to surprising numbers within one hair follicle—ten per follicle is not unheard of—and a large number of D. folliculorum mites seems to go along with skin problems, though this is by no means a reliable rule.
Over the years, considerable evidence has accumulated that Demodex folliculorum may at least play a role in certain skin conditions, particularly papulopustular rosacea. Patients with immunity problems, such as AIDS patients, appear to be particularly susceptible. Symptomatic infestation with demodex mites is called demodicidosis or demodex folliculitis.
While the role of demodex in disease is still unclear, treatment for skin problems in cases where there are many mites present now often includes a topical antiparasitic cream. Treatment successes where the mites were targeted provide further indirect evidence that face mites cause skin problems, at least in some instances.
Read about other skin parasites of humans:
Scabies mite - Sarcoptes scabiei
Dermatobia hominis - Warble Fly
Sources:
“Demodex Mites in Acne Rosacea.” Rooihu, T, and A. L. Kariniemi. J Cutan Pathol. 1998; 25(10):550-2.
Foundations of Parasitology 6th Ed. Roberts, Larry S. and John Janovy Jr. Boston: McGraw Hill, 2000.
Furtive Fauna: A Field Guide to the Creatures Who Live on Us. Knutson, Roger M. New York: Penguin Books, 1992.
“The Significance of Demodex folliculorum Density in Rosacea.” Erbaci, Z. and O. Ozgöztai. Int J Dermatol. 1998; 37(6):421-5.
