Wednesday, October 19, 2016


What is Demodex?
Demodex is an 8-legged, microscopic mite. Two species live on humans: Demodex folliculorum, which are found in the eyelash follicles, and Demodex brevis, which are found in the sebaceous (sweat) and meibomian (oil) glands. These mites live primarily on the face and feed on skin cells and oil in the follicles and glands. They avoid sunlight and live for about 2 to 3 weeks. How common are they? Fairly common in adults (studies report they are found on the skin of 20-80% of adults- that's a pretty wide range and not a super helpful stat...), and nearly 100% of elderly people have the mites on their skin (1). Studies have shown that the prevalence of Demodex increases with age, and Demodex mites are present in higher numbers in those with rosacea, compromised immune systems, and possibly contact lens wearers (23).

Two D. folliculorum on a plucked eyelash (A) and one hanging solo (B)
image: JKMS

Fun (or disgusting) fact: Demodex mites have no anus. Their waste is stored in the gut and expelled when they die, which may cause additional inflammatory response. Shout-out to one of my patients who shared that fact with me. #mypatientsaresmarterthanme

Demodex being teased out of the follicle (arrow) via lash rotation
image: Optometry and Vision Science

What problems can Demodex cause?
Many people have Demodex mites on their skin and have no symptoms or complications. However, Demodex overpopulation (demodicidosis) has been linked to (not necessarily causative of) skin conditions such as blepharitis, rosacea and perioral dermatitis, as well as meibomian gland dysfunction, dry eye, recurrent chalazion, and ocular surface inflammation (45).

Demodex mites can cause problems by clogging hair follicles and sweat ducts, causing abnormal thickening and growth of the epithelial cells at the lid margin. Further, the exoskeleton and waste of the mites can cause an inflammatory response (67). Overpopulation of Demodex mites has been linked to an increase in the presence of certain cell-signaling proteins (cytokines, specifically interleukins) in the tears, which can cause an inflammatory or immunological response (8).

The presence of cylindrical dandruff or "waxy sleeves" around the base of the eyelashes is a very good indicator of demodicidosis. Symptoms may include itching and redness of the lid margin, loss of lashes or misdirected lashes, as well as burning or irritation.

Cylindrical flakes that are highly suggestive of demodex
image: Review of Optometry

How do you get rid of the little buggers?
Frequent scrubbing of the lids with diluted tea tree oil (TTO) was found to be the most effective way to eradicate Demodex and improve patient symptoms (9). The TTO has ingredients (namely, terpinen-4-ol) that kill mites and ticks while also luring the mites out of the hair follicle before they mate (10). There are also lid wipes, scrubs and shampoos containing various concentrations of TTO that can be used for at-home treatment and long-term maintenance. It is best to keep the concentration of TTO at or below 50%; any higher than that may be too irritating (11). Your eye doctor may choose to add an antibiotic and/or steroid ointment or drop to the treatment as indicated, depending on what other symptoms and signs are present.

CliffsNotes: If you suffer from dry, itchy, irritated, red, and/or crusty eyelids, have your optometrist take a look. You MITE (see what I did there?) have a Demodex party going on in your eyelashes. 

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