Microscopic organisms do live in your eyelashes. These tiny inhabitants are mites belonging to the genus Demodex, which are the most common ectoparasites found on the human body and are a normal part of the human skin microbiome. Their existence is usually undetectable, but a significant overgrowth can lead to inflammation and eye discomfort.
Identifying the Eyelash Resident
The two species most commonly found on humans are Demodex folliculorum and Demodex brevis, both of which favor the face and eye area. D. folliculorum is the slightly larger species and resides primarily in the hair follicles of the eyelashes. D. brevis is found deeper within the sebaceous glands and meibomian glands. These mites are elongated with a worm-like appearance and eight short legs. They primarily feed on dead skin cells and sebum, the oily substance naturally produced by the glands in your skin.
The Commensal Life Cycle
The mites share a largely harmless, commensal relationship with their human hosts, meaning they benefit without causing harm by cleaning up excess oil and dead cells. The adult mites mate, and the female then moves deeper to lay eggs inside the follicle or sebaceous gland. The entire life cycle, from egg to larva to adult, is relatively short, lasting approximately two to four weeks. The body’s immune system and natural skin cell turnover generally keep the mite population in check, preventing their numbers from reaching problematic levels.
When Overgrowth Occurs: Symptoms and Conditions
Problems arise when the mite population increases significantly, a condition known as demodicosis. This can be triggered by factors like a compromised immune system, poor eyelid hygiene, or underlying skin conditions such as Rosacea. The rate of infestation naturally increases with age; nearly 100% of people over 70 are estimated to host the mites. This overgrowth can lead to Demodex-related Blepharitis, which is chronic inflammation of the eyelid margin.
A distinctive sign of this condition is the presence of cylindrical dandruff, or collarettes, which are waxy, sleeve-like deposits found at the base of the eyelashes. The mites’ activity and waste products can cause chronic itching, a gritty sensation, or a burning feeling in the eyes. Other symptoms include redness, inflammation, crusting, and in severe cases, the loss of eyelashes (madarosis). The mites can also carry bacteria on their bodies, which contributes to the irritation of the eye area.
Prevention and Management
Maintaining rigorous eyelid hygiene is the primary defense against mite overgrowth and is recommended even for those without symptoms. This includes daily, gentle cleansing of the eyelids and lashes to remove the debris, oil, and dead skin cells the mites feed on. Patients with symptomatic overgrowth should avoid sleeping in eye makeup, as cosmetic residue provides additional food for the mites. For cases of Demodex-related Blepharitis, healthcare providers often recommend specialized lid scrubs, frequently containing tea tree oil or its active ingredient, terpinen-4-ol, which kills the mites. In-office treatments may involve mechanical exfoliation, and for persistent infestations, ophthalmologists or dermatologists may prescribe specific topical medications to reduce mite counts and alleviate chronic inflammation.