When it comes to blepharitis, the gram positive bacteria get all the attention and therapy. However, recent literature suggests that the tiny mite,
Demodex, may be an underappreciated and untreated culprit. In the May 2007 issue of the American Journal of Ophthalmology, Kheirkhah and associates reported success in treating six patients with
Demodex infestation, who had failed the traditional approach of managing ocular rosacea and blepharitis, such as oral tetracycline, topical steroids and antibiotics, and lid hygiene with shampoo.
Demodex is the most common mite that inhabits human skin structures and has a predilection for the sebaceous glands of the face, cheeks, forehead, nose and external ear…..exactly the areas where rosacea manifests. It is diagnosed by epilating an eyelash or two, and examining them under a light microscope at 25X. The same group found that Demodex infestation was highly correlated to cylindrical dandruff at the lash base, which will improve the diagnostic yield when selecting lashes to pluck.
It is thought that the mites trigger inflammation and an immune reaction. Further, the mites block the hair follicle which increases the likelihood of bacterial superinfection. Also, the mites themselves, can have bacteria on them, and be the source of bacterial superinfection.
Demodex infestation is treated by using weekly lid scrubs with 50% tea tree oil and daily lid scrubs with tea tree shampoo for at least six weeks. Tea tree oil is steam distilled from the leaf of Melaleuca alternifolia. It has long been used in traditional aboriginal medicine for various skin maladies. In addition to its anti-mite efficacy, tea tree oil also has antibacterial, antifungal, and anti-inflammatory effects. The senior author, Dr. Scheffer C.G. Tseng, has even applied for a patent for the clinical use of tea tree oil in treating demodicosis.
In addition to tea tree oil, other topical therapies have been tried such as physostigmine or pilocarpine ointments which attack the nervous system of the mites. However, there may be unpleasant side effects such as pupil constriction for the patient. For this reason, I don’t use them.
In my academic practice, I have the fortune of having a dermatology clinic right next door to my office. So, I have been able to manage these challenging patients with the help of my dermatologic colleagues. In addition to tea tree oil derivatives, we have used oral therapy, such as two doses of Ivermectin separated by one week. In addition, for the recalcitrant cases, oral metronidazole may be used over a period of several weeks to months and titrated based on clinical effect. This is a less popular choice for patients because alcohol and metronidazole do not mix, and they may experience flushing and gastrointestinal distress if alcohol is consumed.
So, the next time you have a patient who is not responding to the standard blepharitis therapies, consider looking for Demodex. It just “mite” be the problem.
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