Skin mites are microscopic, eight-legged creatures that live in your hair follicles and oil glands. Two species are exclusive to humans, and nearly everyone carries them. They’re too small to see with the naked eye, they come out at night to move across your skin, and in most people they cause zero problems. But when their numbers spike, they can trigger redness, itching, and skin conditions that mimic rosacea or acne.
The Two Species That Live on You
Humans host exactly two species of skin mite, both in the Demodex family. Demodex folliculorum is the larger of the two, measuring 0.3 to 0.4 millimeters, roughly the width of a fine pencil line. It lives in the upper part of hair follicles, especially in eyelash follicles and facial hair. Demodex brevis is smaller (0.2 to 0.3 mm), and it burrows deeper into oil glands and the specialized glands along your eyelid margins.
Both have semi-transparent, worm-like bodies made of two fused segments, with eight stubby legs clustered near the head. Their bodies are covered in tiny scales that anchor them inside follicles, and they have pin-like mouthparts designed to pierce and consume skin cells and the oily sebum your skin produces. D. folliculorum is far more common and tends to cluster in groups inside a single follicle. D. brevis is typically found alone, tucked deep inside an oil gland.
How Common They Are
Skin mites are essentially universal in older adults. About 84% of people over 60 carry them, and that number reaches 100% in people over 70. Children, by contrast, rarely have them. One survey of healthy children aged 3 to 14 found mites in only 12%. The likely reason is sebum: children’s oil glands are far less active, so there’s less food for mites. As sebum production ramps up through puberty and adulthood, mite populations grow with it.
You acquire them through skin-to-skin contact. Babies are born without them and pick them up from parents, caregivers, and close family members during normal contact like holding, kissing, and sharing pillows. Once they colonize your skin, they’re there for life.
What They Eat and How They Live
Both species feed on the oily secretions your skin produces. D. folliculorum sits near the surface of a follicle and eats skin cells and sebum. D. brevis goes deeper and feeds directly on the cells of oil glands themselves. The mites also carry a fat-digesting enzyme that breaks down the triglycerides in sebum into free fatty acids, which may contribute to skin irritation when mite numbers are high.
Their entire life cycle, from egg to larva to nymph to adult, plays out inside your follicles. Adults emerge at night to crawl across the skin surface to mate, then return to a follicle to lay eggs. They move slowly, covering only about 8 to 16 millimeters per hour. One unusual feature: these mites have no anus. Waste accumulates inside their bodies throughout their lives. When they die, they decompose inside the follicle and release all that stored waste at once, along with bacteria they’ve been carrying internally.
When Mites Cause Problems
Simply having mites on your skin is normal and not a diagnosis. With sensitive enough testing, nearly 100% of adult skin samples contain Demodex. What matters is density. Below about five mites per square centimeter of skin, or fewer than three to five per hair follicle, they’re considered harmless passengers. Problems start when their population grows beyond that threshold, a condition called demodicosis.
People with mite overgrowth most commonly notice facial redness (seen in about 83% of cases), flaky or scaly skin (65%), dryness (56%), and sometimes small pimple-like bumps (22%). The cheeks, forehead, chin, and nose are the most affected areas, since these zones produce the most oil. Some people experience roughness you can feel by running a finger across the skin, or a greasy texture despite the skin looking dry. Itching is reported less often than you might expect, showing up in only about 6% of diagnosed cases.
The symptoms overlap heavily with rosacea and seborrheic dermatitis, which is why mite overgrowth often goes unrecognized. In fact, people with rosacea carry dramatically more mites than people without it. Studies comparing skin biopsies found an average of 10.8 mites per square centimeter in rosacea patients versus just 0.7 in healthy controls. People with chronic eyelid inflammation (blepharitis) show a similar pattern: roughly 0.69 mites per eyelash compared to 0.08 in unaffected people.
The Bacteria Connection
Part of the reason high mite numbers cause inflammation involves a bacterium called Bacillus oleronius that lives symbiotically inside the mites’ digestive tracts. While the mites are alive, the bacteria stay contained. When the mites die and decompose inside a follicle, they release a burst of bacterial proteins into surrounding tissue. Your immune system recognizes these proteins as foreign and mounts an inflammatory response, attracting immune cells to the area. This may explain why rosacea flares come and go: each cycle of mite death triggers a fresh wave of inflammation.
What Triggers Overgrowth
Anything that suppresses your immune system or increases oil production can let mite populations grow unchecked. Immunosuppressive medications, prolonged corticosteroid use (especially on the face), and conditions like HIV or leukemia are well-documented risk factors. Oily skin naturally supports larger mite colonies. Some evidence also links overgrowth to heavy use of thick facial creams or makeup that creates a richer food supply on the skin surface.
How Overgrowth Is Diagnosed
A dermatologist can check for mite overgrowth through a simple skin scraping or by pulling a few eyelashes and examining them under a microscope. Adhesive tape pressed onto the skin can also pick up mites living near the surface. The key diagnostic factor is not whether mites are present (they almost certainly are) but how many there are per follicle or per square centimeter of skin.
Treatment Options
When mite populations need to be reduced, the most common topical approaches use ingredients that are directly toxic to the mites. Prescription creams containing ivermectin or permethrin are standard first-line treatments. Metronidazole gel is another option, often used when the presentation looks like rosacea. For stubborn cases that don’t respond to topical treatment, oral ivermectin can be taken in one or two doses spaced a week apart. In rare refractory cases, low-dose isotretinoin (a drug that shrinks oil glands) has been used successfully, essentially starving the mites by cutting off their food supply.
For milder cases or eyelid-specific problems, tea tree oil has shown genuine effectiveness. The active component responsible for killing Demodex is terpinen-4-ol, which is lethal to the mites at just a 1% concentration. Several other compounds in tea tree oil also kill mites at concentrations above 2.5%. Tea tree oil lid scrubs and wipes are widely available for managing mite-related eyelid irritation, though the oil needs to be properly diluted since full-strength tea tree oil can burn skin.
Treatment typically needs to continue for several weeks because the medications kill adult mites but not always the eggs already laid deep in follicles. A second generation of mites can hatch after treatment stops, which is why repeated applications or follow-up doses are standard.