Demodex blepharitis is a common inflammatory condition of the eyelids caused by microscopic mites, known as Demodex, which are a natural part of the skin’s ecosystem. These mites typically live harmlessly in and around the hair follicles on human skin. However, when the population of these mites on the eyelids and eyelashes increases, it can lead to irritation, redness, and discomfort.
Causes and Risk Factors of Demodex Mite Overgrowth
Demodex blepharitis is caused by the overpopulation of two specific mite species: Demodex folliculorum and Demodex brevis. D. folliculorum resides within the eyelash follicles, while D. brevis burrows into the sebaceous glands connected to these follicles. This overpopulation can lead to mechanical blockage of glands, direct tissue damage, and inflammatory reactions to their waste products and the bacteria they carry.
Advancing age is a primary risk factor, with mite density increasing as people get older; nearly all adults over 70 are found to have these mites. A compromised immune system, whether due to chronic diseases like diabetes, immunosuppressive therapies, or conditions like HIV, can also make an individual more susceptible. Co-existing skin conditions, particularly rosacea, are strongly associated with a higher density of Demodex mites. Lifestyle and environmental elements, such as poor eyelid hygiene, higher alcohol intake, and increased sun exposure, may also contribute.
Recognizing the Symptoms
The symptoms of Demodex blepharitis can significantly overlap with other eye conditions, making self-diagnosis difficult. A primary symptom is persistent itching of the eyelids, which characteristically worsens in the morning. This timing is thought to be related to the mites’ nocturnal activity of mating and laying eggs on the skin surface before burrowing back into the follicles.
Patients frequently experience redness and swelling along the eyelid margins, accompanied by a burning or stinging sensation. A gritty feeling, as if a foreign object is in the eye, is also common. A specific sign is “cylindrical dandruff,” a waxy, sleeve-like debris that wraps around the base of the eyelashes. This material is composed of the mites’ waste, their eggs, and inflamed skin cells. In more advanced cases, the condition can lead to the loss or misdirection of eyelashes (madarosis) and even blurry vision.
Diagnosis by an Eye Doctor
Diagnosis is made by an optometrist or ophthalmologist through a clinical examination. The doctor uses a slit-lamp examination, where a high-powered microscope is used to closely inspect the eyelids and eyelashes. During this exam, the patient is often asked to look down, which allows the doctor a clear view of the base of the upper lashes to spot the cylindrical dandruff. The presence of these collarettes is considered a sign specifically characteristic of Demodex infestation.
While visual inspection is often sufficient, a definitive diagnosis may involve eyelash epilation. The eye doctor carefully removes a few eyelashes to be examined under a laboratory microscope. This allows for direct visualization and counting of the mites on the sampled lashes. Confirming the mite density helps to differentiate Demodex blepharitis from other forms of eyelid inflammation, such as those caused by bacteria or allergies.
Treatment and Management
Treatment combines at-home care and professional treatments aimed at reducing the mite population and alleviating inflammation. Consistent eyelid hygiene is a key part of at-home management. This includes daily cleaning of the eyelids with specialized cleansers, such as those containing tea tree oil or its active component, terpinen-4-ol. Hypochlorous acid sprays are another option. It is also advisable to avoid oil-based cosmetics and to regularly wash bedding and towels to prevent re-infestation.
For more persistent cases, an eye doctor may recommend in-office procedures. Microblepharoexfoliation, using a device like BlephEx, is a mechanical process that scrubs the eyelid margins to remove mites, their eggs, and the biofilm they create. The FDA-approved prescription medication, Lotilaner ophthalmic solution 0.25% (brand name Xdemvy), is another treatment. This eye drop kills Demodex mites by targeting their nervous system, causing paralysis and death. The standard treatment course is one drop in each eye, twice daily, for six weeks.