However, Demodex mites have also been found in young adults, and a recent study conducted in Hungary that included 96 healthy adults found that certain risk factors influence the presence of mites.2 Demodex mites were found more frequently in men and older adults, and patients who wear makeup were less likely to have Demodex on their skin.
One way to prevent Demodex infestation is good hygiene. Because the eye is surrounded by bone, it can be difficult to clean. For this reason, once Demodex infestation is established on the face, it is likely to spread to the eyelids and eyelashes, leading to blepharitis.
“Demodex is quite common and is age-dependent in most patients,” says Scheffer C.G. Tseng, MD, PhD, director of the Ocular Surface Center in Miami. “The older you are, the higher the chance you may have some mites on your body. Furthermore, the eye area is often not cleaned well. The eye is surrounded by the brow, cheekbone and nose, which are the protruding, bony parts of the face. The eye surface is in the valley of the surrounding bony area. People don’t typically clean the socket as part of their body hygiene. As a result, this increases the chance of infestation as people get older.”
Two different Demodex species have been found to cause blepharitis: Demodex folliculorum can cause anterior blepharitis associated with disorders of the eyelashes, and Demodex brevis can cause posterior blepharitis with meibomian gland dysfunction and keratoconjunctivitis.1
Because Demodex can be found in asymptomatic patients, it is often overlooked in the differential diagnosis of corneal and external disease. “In our experience, Demodex is one of the often overlooked conditions in the eye because people don’t think about it,” says Dr. Tseng. “Many physicians do not recognize this as a potential cause of blepharitis, and many people tend to trivialize it. They don’t think it’s a big deal because they just feel a little bit of itching or irritation. As you get older, the disease can get out of control. Sometimes, it becomes a conjunctival and corneal disease. We believe this is a disease that people should pay a great deal of attention to, as independent studies have shown that blepharitis affects as many as 70 to 80 million Americans, and upwards of 80 percent of those patients could have Demodex mites. It remains unclear how mites might cause eye inflammation. Besides causing direct damage to the hair follicles/lashes and meibomian glands, mites can carry bacteria into the host and become like a vector. They can even introduce bacillus to patients, which is hard to treat.”
While some patients with Demodex are not bothered by it, patients with rosacea often experience symptoms. “Everyone has staph bacteria on their skin, but not everyone gets a staph infection,” says Steven Safran, MD, an ophthalmologist in private practice in Lawrenceville, N.J. “Patients with rosacea are allergic to bacillus in the Demodex organism called Bacillus oleronius. Some people have Demodex on their skin, and they don’t seem to be too bothered by it. Then, other people have some Demodex, and they are very bothered by it.”
“Most Demodex are on the eyelid or on the skin around the eye,” Dr. Safran says. “You don’t necessarily see it until you know how to look for it. I’ve seen patients with very hot eyes with inflammation where I didn’t see Demodex on the eyelashes but I found it in the skin around the lid. You may not find it where you think you are going to find it. You can’t just pull lashes and say, ‘let’s count the Demodex.’ They live at the base of the lashes. In many patients, you will pull the lashes, and you won’t see the Demodex. You have to tease them out. I know how to find them at the slit-lamp, so I don’t have to look under a microscope. The reason I put the lashes under a microscope is to show patients what they have. Otherwise, they don’t necessarily understand it or believe you. They might go for a second opinion to someone who has not heard of this problem.” Fortunately, the number of ophthalmologists who are knowledgeable about Demodex infestation is on the rise. “Five years ago, if I told a patient that he or she had mites causing blepharitis and she went to a place like Wills or Hopkins, the possibility existed that the patient could be told that the doctor had ‘never heard of such a thing,’ ” says Dr. Safran. “Now, more people are aware of it. If you look at the dermatology literature, for example, there are many articles showing the association between rosacea and Demodex. We know that rosacea is associated with blepharitis. Rosacea is associated with Demodex, and blepharitis is associated with Demodex. It is pretty clear to me that there is a circle here where both rosacea and blepharitis are associated with Demodex. Demodex is probably at the root of a lot of these patients’ problems. When we treat their Demodex with systemic and topical medications, not just their eyes get better, but, in most cases, their rosacea vastly improves.”
According to Dr. Tseng, one reliable method of identifying Demodex is looking for cylindrical dandruff. “Some patients may not present with cylindrical dandruff, but they may have mites. The most reliable method to diagnose Demodex is the sampling of the lashes and looking at them under the microscope,” Dr. Tseng adds.
The good news is that the lifespan of the Demodex mite is short (approximately 19 to 23 days). The bad news is that they mate and continue to grow in number if you don’t remove them all.
“If you have an effective means to prevent them from mating through hygiene, then the population will be under control and eventually eradicated,” Dr. Tseng says. “The problem is that the eye socket, as I said, is not an area where hygiene is routinely practiced, so the mites tend to flourish in numbers. Once they get out of control, they cause blepharitis.”
Lid scrub with tea tree oil has been found to clean dandruff from the lash root and also to stimulate embedded mites to migrate out of the skin. Typically, a daily lid scrub with 50% tea tree oil and lid massage with 5% tea tree oil ointment will resolve ocular Demodex infestation.
“Specifically for the eye, there are a lot of so-called lid scrub cleansing agents on the market that are over-the-counter,” Dr. Tseng says. “We haven’t found them to be effective in killing mites. We use 75% alcohol to clean our hands or sterilize our instruments before surgery, but even that won’t kill mites. We continued to search for a natural yet effective solution and found tea tree oil as a potential killing agent. A few years ago, we received an NIH research grant to further determine the active component in the tea tree oil. We are now formulating the active component into a single-use, disposable cleansing pad called Cliradex, which will be commercially available in the next few months.” (Dr. Tseng is the inventor and patent holder of the product.)
Cliradex is a two-part system that includes a cleansing eyelash scrub and a cleansing skin cream. The scrub is used to stimulate the mites out from deep skin and cause direct killing, and the cream prevents the mites from mating.
According to Dr. Safran, in addition to tea tree oil, permethrin and ivermectin can be used as treatment. “We don’t have the world’s greatest treatments for this,” he says. “Right now, as a topical treatment, we use tea tree oil as the mainstay of treatment. We treat deep into the patients’ lashes and into the skin around the lashes and the brows every four to five days. We train the patients to treat themselves so they can maintain the process. Sometimes, we need a steroid to quiet things down. We’ll use topical permethrin 5% to the whole facial area around the eyelids every four days or so. We also use oral ivermectin, which has been shown to be helpful. I started using that based on the veterinary literature. Often, the veterinarians get first crack at a medication that has human application, such as was the case with topical cyclosporine for dry eye. Veterinarians use ivermectin to treat demodectic mange. Not every dog that is exposed to Demodex ends up with mange. There is a variable host response, and that is something that we see in humans as well.”
A recent study conducted in Brazil found that oral ivermectin effectively reduced the number of Demodex folliculorum found in the lashes of patients with refractory blepharitis. This study included 24 eyes of 12 patients with refractory posterior blepharitis with Demodex folliculorum in the lash samples. Patients were given one dose of oral ivermectin (200 µg/kg) and were told to repeat the treatment after seven days. After treatment, fewer Demodex folliculorum were found in the lashes, and average values of Schirmer I test results and tear breakup time improved.
As mentioned earlier with regard to patients’ bedding, heat effectively kills Demodex. Dr. Safran is currently evaluating radiofrequency and heat as potential treatments. “I’m currently exploring using the Pelleve radiofrequency system off-label to treat blepharitis/Demodex,” he says. [The manufacturer] Ellman made special hand pieces for me so that I can treat patients right up to the lid margin and try to kill Demodex with radiofrequency energy/heat. I’m not crazy about treating patients with tea tree oil. It’s messy, it’s smelly and it stings. I don’t think it’s the best way to kill these things, but it’s the best way we have. If you don’t stay on top of it, ultimately, they come right back,” he says.
The importance of hygiene cannot be overemphasized. “Patients have to shampoo their hair. Many little old ladies go to the beauty salon once every week or two and get their hair done and then shellacked in place,” Dr. Safran adds. “You are not going to get rid of Demodex if you can’t get them to shampoo their hair. We give them tea tree oil shampoo, and if they refuse to use that, there is nothing I can do for them. You can’t just treat the lid because they will come right back.” REVIEW
1. Liu J, Sheha H, Tseng SCG. Pathogenic role of Demodex mites in blepharitis. Curr Opin Allerg Clin Immunol 2010;10:505-510.
2. Horvath A, Neubrandt DM, Ghidan A, Nagy K. Risk factors and prevalence of Demodex mites in young adults. Acta Microbiol Immunol Hung 2011;58(2):145-155.
3. Holzchuh FG, Hida RY, Moscovici BK, et al. Clinical treatment of ocular Demodex folliculorum by systemic ivermectin. Is J Ophthalmic 2011;151(6):1030-1034.