Microscopic organisms are common inhabitants of the human body, and the area around your eyes is no exception. This presence is a natural biological occurrence, not necessarily a sign of poor hygiene or illness. These tiny residents are generally kept in check by your body’s natural defenses and are considered part of the normal human biome.
Identifying the Eyelash Mite: Demodex
The microscopic creatures found near your eyelashes belong to the genus Demodex, specifically two species: Demodex folliculorum and Demodex brevis. These mites are not insects but are tiny arachnids, meaning they are related to spiders and ticks. They are completely invisible to the naked eye, measuring only about 0.3 to 0.4 millimeters in length, which is less than half the size of a grain of salt.
The two species occupy slightly different niches within the skin around your eyes. D. folliculorum primarily lives inside the hair follicles of your eyelashes and eyebrows, often aggregating in groups, while the smaller species, D. brevis, burrows deeper, residing within the sebaceous glands that connect to the hair follicles. Both species feed on dead skin cells and the oily secretions, called sebum, produced by these glands.
Prevalence and Transmission
The presence of Demodex mites is remarkably widespread, making them a nearly universal associate of adult humans. Studies suggest that nearly 100% of adults harbor at least one species of these mites. While children and young adults have a lower rate of colonization, the prevalence increases significantly with age, with a high percentage of people over 60 having the mites.
The mites are easily transferred between people through routine close physical contact, such as touching or sleeping near one another. Sharing items that come into contact with the face, like towels or makeup, can also facilitate transmission. The increasing prevalence with age is related to changes in the skin’s oil production and a gradual decrease in the body’s immune response, which allows the mite population to grow more easily.
When Demodex Mites Cause Symptoms
While the mites are usually harmless commensals, an overpopulation or imbalance can lead to a condition known as demodicosis. This occurs when the mite density becomes too high, often triggered by a compromised immune system or underlying skin conditions like rosacea. The mites can cause irritation by mechanically obstructing the oil glands, which disrupts the normal flow of tears.
The most common condition associated with a Demodex overgrowth is blepharitis, which is inflammation of the eyelid margins. Symptoms often include chronic itching, a burning sensation, and redness along the lash line. A distinctive sign of an infestation is the presence of “cylindrical dandruff,” a flaky, crusty material that builds up at the base of the eyelashes. In more advanced cases, the inflammation can lead to chronic dry eye symptoms, a feeling of grittiness, or even the loss of eyelashes (madarosis).
Eyelash and Eyelid Hygiene
Controlling the Demodex population is primarily achieved through consistent and targeted eyelid hygiene practices. The goal is not to eliminate the mites entirely, but to keep their numbers low enough to prevent inflammation and symptoms. This involves daily cleansing of the eyelids and lashes to remove the sebum and debris that the mites feed on.
Specialized eyelid cleansers, often available as wipes or foams, are effective for daily use. Many of these products contain a diluted concentration of tea tree oil, which is known to be toxic to the mites. Applying a warm compress to the eyelids for several minutes can also help loosen crusty buildup and clear blocked oil glands, reducing the mites’ food source. If symptoms persist despite consistent hygiene, an eye care professional can offer in-office treatments or prescription medications designed to further reduce the mite count.