- Which Types of Demodex Mites Affect Humans?
- Why Do Demodex Mites Live in Our Skin?
- Can Demodex Mites Cause Problems?
- Do Demodex Mites Contribute to Acne?
- What Treatments Are Available for Demodex Mites?
- The Bottom Line
Demodex mites are tiny, insect-like organisms that live in human hair follicles and sebaceous (skin oil) glands, where they lay their eggs and ultimately die. This entire life cycle is only a few weeks.1–4They are technically visible, but we never see them because in addition to being extremely small, they are colorless. They also usually only move around at night, and they move extremely slowly, about 1 cm/hr.
Which Types of Demodex Mites Affect Humans?
There are more than 100 types of Demodex mites, but only two types are abundant on the human body.
- Demodex folliculorum (D. folliculorum) live in hair follicles. They are approximately 0.3–0.4 mm long.
- Demodex brevis (D. brevis) live in sebaceous (skin oil) glands. They are about half the size of D. folliculorum.1–4
Why Do Demodex Mites Live in Our Skin?
Demodex mites are present in the hair follicles and sebaceous glands of all humans, though some people carry more mites than others.4Researchers do not know exactly why these mites live in our skin. We most likely evolved in a symbiotic (mutually beneficial) relationship with the mites, and they have probably coexisted with us for a long time. One theory is that, along with beneficial bacteria that also live on the skin, Demodex mites may protect human skin against harmful bacteria. The mites contain an enzyme (substance that speeds chemical reactions) that breaks down various skin oils into acids. This creates a mildly acidic environment on the skin in which harmful bacteria cannot thrive.4,5
Can Demodex Mites Cause Problems?
While Demodex mites are present on all humans and are generally not harmful, they can cause problems in some people. Because the mites cannot digest what they consume, they rely on another symbiotic relationship with bacteria that help them digest their food. They also lack an anus and cannot eliminate their waste. Because of these peculiarities, Demodex mites release a large amount of bacteria and waste into the skin immediately when they die, and this may provoke an immune response and inflammation in their human host. Demodex mites also appear to contribute to several skin diseases, and researchers call such skin diseases caused by these mites demodicoses, the singular of which is demodicosis.3,4,6 Acne is not a demodicosis. However, acne is an inflammatory disease, so there is some speculation that in certain cases, they might add to the severity of acne symptoms.
Why Demodex mites cause problems in some people but not in others remains unknown. However, researchers are finding that when people have an excess of mites in their skin, this leads to more skin diseases. In addition, in people who develop demodicoses, the mites often penetrate deeper into the skin, rather than staying closer to the surface. Finally, there may be a relationship with immune system function: people with impaired immune systems are more prone to developing demodicoses than people with healthy immune systems.4
Scientists have proposed several ways in which Demodex mites might contribute to skin diseases.
- They might block hair follicles and skin oil gland ducts.
- They may provoke an immune reaction and inflammation. In some people, the immune system might regard the mites as “invaders” and attack them.
- They may transmit a type of bacteria called Bacillus oleronius. This bacteria produces substances that can cause inflammation. When the Demodex mites die, the bacteria and the substances it produces are released into the hair follicles or sebaceous glands and may cause skin inflammation.6–9
Do Demodex Mites Contribute to Acne?
Although Demodex mites appear to contribute to several other skin diseases, it is uncertain whether they play a role in acne.
A 2006 study in the Journal of the European Academy of Dermatology and Venereology found no relationship between acne and D. folliculorum mites: in 102 young adults the prevalence of D. folliculorum was not significant between groups with and without acne, and there were actually more mites in the people who were not affected by acne. There was no significant difference between the prevalence of these mites and the severity of acne lesions either. The authors concluded, “[T]he presence of D. folliculorum does not appear to be related to acne vulgaris.”10This study did not consider D. brevis, so we cannot draw conclusions regarding its relationship to acne.
On the other hand, a 2012 meta-analysis (an analysis of several studies in an attempt to draw one conclusion) in the Journal of Zhejiang University SCIENCE B found an association between Demodex mites and acne, though this connection was not as strong as that between Demodex mites and rosacea.11This study did not indicate whether D. folliculorum or D. brevis mites were investigated.
Based on these two studies, we cannot say whether Demodex mites affect acne development. More research is necessary to draw any conclusions.
What Treatments Are Available for Demodex Mites?
If you have acne, the first line of defense is not treating the skin for Demodex mites. Everyone’s skin contains Demodex mites, and the mere presence of the mites is not a problem. However, for people who experience demodicoses like the ones described above, there are several treatments that can eliminate them. Treatment usually includes medications with antiprotozoal (protozoa are single-cell organisms), insecticide (poisonous to a variety of insects), and/or acaricide (poisonous to mites and ticks) properties. The most common medications for eliminating these mites are:
- Ivermectin (an acaricide medication that is effective against many kinds of parasites)
- Permethrin (an insecticide medication)
- Metronidazole (an antibiotic and antiprotozoal medication)6,12,13
Several studies suggest that treatment with these medications help clear Demodex-related skin diseases. In addition, some research indicates that tea tree oil is effective against Demodex mites. Tea tree oil is also moderately effective against acne. Here are a few studies that show how these medications and tea tree oil can eliminate skin diseases caused by Demodex mites.14
A 1999 study in the Journal of the American Academy of Dermatology found that a combination of ivermectin and permethrin successfully treated a case of rosacea-like demodicosis.12
A 2009 study in the Journal of the American Academy of Dermatology found that a combination of acaricides and antiprotozoals cleared up various demodicoses.6
A 2005 study in the British Journal of Ophthalmology found that tea tree oil was effective in eliminating ocular (eye) Demodex mites.14
The Bottom Line
While it's interesting to learn about Demodex mites, it is best not to look to them as a primary concern when it comes to acne. There are other proven treatments for acne that address the real concerns regarding acne and consistently work to help clear the skin.