What Are Demodex Mites?
Last updated: January 2023
While it may be unnerving to think about, many of the cells in our bodies are not actually ours. We host a complex group of microflora, including bacteria, viruses, fungi, and microscopic insects. And many of these tiny organisms benefit us.1
Scientists believe we each host more than 100 trillion cells that are not ours. One of these microflora is called the Demodex mite. Almost everyone has Demodex mites living on their body. The mites are incredibly small, measuring from about one-fifth to two-fifths of a millimeter long.1-3
There are 2 common types of Demodex mites:4
- Demodex folliculorum – This is the larger of the 2 common Demodex mites. It generally lives on hair follicles, such as the eyelashes.
- Demodex brevis – These smaller mites tend to live on glands that produce oil. On the skin, these are sebaceous glands. There are also oil-producing glands in the eyes called the Meibomian glands.
Most people will go their entire life without ever knowing they have Demodex mites living on them. But some people will end up with a Demodex infestation, called demodicosis. This is when the number of Demodex mites multiplies out of control, and they become parasites.2
Who is at risk for demodicosis?
Demodicosis is not common. It usually occurs in people who have issues with their immune system not working properly. This can be due to:3
- Drugs that suppress the immune system (immunosuppressants, such as the ones taken after an organ transplant or to treat an autoimmune disease)
Demodicosis is more common in older people than in younger people. If you are someone who takes care of a senior, you may also be at higher risk for demodicosis.2
What does demodicosis look like?
Demodicosis will look different depending on the mite that is causing the infestation. Demodex folliculorum will most often cause a condition called blepharitis. This may look like dandruff on the base of the eyelashes. It may also cause:2,4
- Swelling and irritation of the eyelids
- Feeling like something is in your eye (foreign body sensation), but not finding anything
- Eyes that itch, burn, weep or tear
- Crusting of the eyelashes
Demodex brevis infestations are responsible for Meibomian gland dysfunction. These mites can block the Meibomian gland. This can cause swelling of the Meibomian glands and can lead to a sty (chalazion). Meibomian gland dysfunction can also lead to dry eye.4
How is demodicosis treated?
Unless you have an infestation of Demodex mites, there is no reason to treat them. There are a few treatments for demodicosis, but the one that is most often recommended is tea tree oil. It is important that you do not try to treat demodicosis at home. Tea tree oil can be an eye irritant and should only be used under the supervision of your eye doctor.2,4
A few things to keep in mind when you start treatment for demodicosis: The point of the treatments is to reduce the number of Demodex mites, not to get rid of them completely. Treatment for demodicosis is a long road. Demodicosis is considered a long-term (chronic) condition. The goal of treatment is to reduce symptoms.4
If you are concerned that you may have demodicosis, you should contact your eye doctor. They can test for Demodex mites, as well as help you find your best treatment options.4
If you are being treated for demodicosis and are struggling with your treatments, talk to your eye care team. It is important to continue treatment for demodicosis. And your team may be able to help you with issues you are having with your treatment.4
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