Eyelids that are persistently red, inflamed or itchy are signs of a common eye condition called blepharitis. Sometimes, this is caused by an excess of bacteria or clogged oil glands at the base of the eyelashes.
Other times, it may result from an over-population of microscopic mites living inside the eyelash follicles. Known as Demodex, these bugs are also associated with the skin condition rosacea. Recent studies have suggested that anywhere from 42% to 81% of people with blepharitis also have an infestation of Demodex.
Here’s what physicians know about these invisible bugs, and how they can be diagnosed and treated.
Almost Everyone Has Demodex Mites
Two different types of Demodex mites live on the human body. Measuring approximately 0.3 millimeters long, these eight-legged critters are too small to see with the naked eye.
“They are an inhabitant of the skin’s normal microbiome; almost everyone has some Demodex,” said Gerami D. Seitzman, MD, corneal and external disease specialist at University of California San Francisco, CA. The bugs burrow into our hair follicles, where they feast on dead skin cells and sebum. At night, they crawl out to mate and lay their eggs. Demodex have a life span of approximately two to three weeks.
When Mites Become a Problem
Although they have long been considered a friendly bystander of normal skin, sometimes Demodex mites can overpopulate. On the eyelids, a high density of Demodex has been connected to chronic blepharitis as well as other eye conditions. Ophthalmologists haven’t yet reached a consensus on what amount of mites is “normal,” because sometimes large numbers of mites can be found on people who are healthy and have no symptoms.
Even so, a growing number of ophthalmologists believe Demodex may be getting overlooked in patients. This may be true because doctors are not yet clear what comes first: an inflammatory eye condition that allows mites to proliferate, or an out-of-control mite population that brings on an inflammatory eye condition. Also, the mites are easy to miss if doctors aren’t specifically looking for them.
Demodex should be investigated if you have chronic blepharitis symptoms that aren’t responding to standard treatments like warm compresses and eyelid scrubs. “Redness, inflammation, itching, recurrent styes, lash loss and/or trichiasis may be clues that Demodex is a culprit,” said Dr. Seitzman.
How is Demodex Diagnosed?
The definitive way to confirm Demodex is by seeing the mites on pulled eyelashes under a special kind of microscope. However, not all ophthalmologists have the right type of microscope in their offices.
That’s why most eye doctors will make a probable diagnosis by looking for “cylindrical sleeves” on your eyelashes. These are waxy debris that hug tightly to the base of the eyelash. They are made out of a mixture of mite waste and inflammatory skin fragments.
Your ophthalmologist will check for sleeves by using a slit lamp to zoom into the base of your upper eyelashes while you gently close your eyelids. If you receive a Demodex diagnosis, rest assured that it is not related to personal hygiene, and you should not feel embarrassed.
Current Treatments for Demodex
The first line of treatment for ocular Demodex is usually an over-the-counter topical medicine with a low concentration of tea tree oil or hypochlorous-based acid. This can come in the form of a scrub, spray or cleansing wipe (i.e., OCuSOFT, Oust, and Cliradex). Tea tree oil has antimicrobial, antifungal, antiviral, antiseptic, and acaricidal properties that work against the bugs. These topical treatments should be used one to two times per day for one to three months. They may be irritating to some eyes. Your doctor may also prescribe a topical steroid to help reduce inflammation.
Sometimes, stronger medications are needed to gain more symptom relief and better control of the mites. Some ophthalmologists will prescribe anti-parasitic medications approved for the treatment of rosacea, such as ivermectin and metronidazole, as off-label treatments for Demodex. These can be taken in ointment form (as a bedtime scrub) or in pill form. Sometimes they are prescribed in combination. The doctor may complement an oral treatment with a lid scrub to clean the eyelash margin. These off label therapies may have more bothersome side effects that your doctor will discuss with you, including gastrointestinal discomfort, nausea or diarrhea. Adult patients who also have rosacea may be prescribed the antibiotic doxycycline in addition to these other therapies.
It’s important to stick closely to your prescribed treatment regimen and follow-up with your ophthalmologist if you experience any unwanted symptoms.
An FDA-Approved Treatment on the Horizon
A new drug in Phase 3 clinical trials might soon become the first FDA-approved treatment for Demodex blepharitis. TP-03 by Tarsus Pharmaceuticals works by paralyzing the nervous system of the mites. In a Phase 2/3 clinical trial, researchers reported that patients treated with TP-03 daily for four weeks had statistically significant reductions in mite numbers and the treatment was well tolerated.