# Demodex
**Demodex** is a genus of microscopic mites that live in the hair follicles and sebaceous glands of mammals; the two species found on humans, *Demodex folliculorum* and *Demodex brevis*, are permanent residents of human skin and the only permanent human ectoparasites.[1](https://pubmed.ncbi.nlm.nih.gov/25666117/) • [2](https://pmc.ncbi.nlm.nih.gov/articles/PMC5522688/) In most people the mites cause no symptoms, but overgrowth is associated with demodicosis, rosacea, and blepharitis.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites)
| Key fact | Detail |
|---|---|
| Human species | *D. folliculorum* (about 0.3–0.4 mm, in hair follicles) and *D. brevis* (about 0.2–0.3 mm, in sebaceous glands)[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC2906820/) |
| Life cycle | 14–18 days, spent entirely on the host[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC5522688/) |
| Prevalence | Molecular detection found Demodex DNA in 100% of sampled adults over 18 years of age[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4146604/) |
| Rosacea association | Meta-analysis of 23 case-control studies (1513 rosacea patients): odds ratio for infestation 9.039 (95% CI 4.827–16.925); density standardized mean difference 1.617 (95% CI 1.090–2.145)[6](https://www.sciencedirect.com/science/article/pii/S0190962217304292) |
| Causality status | Hill's criteria do not support a causative role in rosacea; mites are a non-necessary, non-sufficient causal factor for certain forms[1](https://pubmed.ncbi.nlm.nih.gov/25666117/) |
| Demodicosis threshold | Diagnosis requires compatible clinical signs and a mite density above 5 per cm²[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC5383737/) |
| Approved drug | Lotilaner ophthalmic solution 0.25% (XDEMVY), FDA approved July 24, 2023 for Demodex blepharitis[8](https://www.fda.gov/drugs/drug-trials-snapshots/drug-trials-snapshots-xdemvy) |
## Biology and morphology
Demodex mites are arachnids with elongated, two-segmented, slightly transparent bodies covered with scales; the front segment carries eight legs and a mouth.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites) The larger *D. folliculorum* lives in clusters in the hair follicle, above the sebaceous gland, where it appears to ingest skin cell contents, while the smaller, spindle-shaped *D. brevis* resides solitarily in the sebaceous gland, typically at densities of one to a few mites per gland, feeding on sebum.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC2906820/) • [5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4146604/) Because adult mites have a limited life cycle, expansion within a host depends on successful copulation by adult males and females at the opening of the hair follicle near the skin surface.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC2906820/) The mites are most active at night, emerging from pores to feed, mate, and lay eggs.[9](https://www.marieclaire.co.uk/beauty/skincare/demodex-skin-mites)
About 140 species or subspecies of Demodex have been identified worldwide across 11 orders of mammals, including humans.[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC5522688/) The mites are host-specific, and the human species cannot currently be cultured in vitro to infect other animal hosts.[10](https://pubmed.ncbi.nlm.nih.gov/37848012/)
## Discovery and history
Human skin Demodex mites were first seen and mentioned in print by Jacob Henle in Zurich in 1841, and were correctly classified as a mite by the dermatologist Carl Gustav Theodor Simon in Berlin in 1842, who named the organism *Acarus folliculorum* after finding it in the skin follicles of the nose.[11](https://onlinelibrary.wiley.com/doi/10.1111/bjd.12850/full) The zoologist [Richard Owen](https://www.edgepedia.org/richard-owen) designated the genus name "Demodex" in 1843, drawing on Greek words for lard and a boring worm to describe the mite's form and preferred location.[12](https://www.duvaryayinlari.com/Webkontrol/IcerikYonetimi/Dosyalar/theoretical-and-applied-approaches-in-health-sciences_icerik_g4619_WaGO9V7S.pdf) The two human species were characterized in detail by Desch and Nutting in 1972, who established that *D. brevis* survives in the sebaceous glands of human skin.[12](https://www.duvaryayinlari.com/Webkontrol/IcerikYonetimi/Dosyalar/theoretical-and-applied-approaches-in-health-sciences_icerik_g4619_WaGO9V7S.pdf)
## How common are the mites
Visual methods, which sample only small patches of skin, suggest that roughly 3–55% of people harbor Demodex, with most studies in the range of 10–20%.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4146604/) Molecular detection changes this picture substantially. In a 2014 study using PCR of sebum samples, Demodex 16S rDNA was amplified from 100% of adults over 18 years of age, while detectability in 18-year-olds was lower at 70%; postmortem studies have likewise found mites on all adult cadavers.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4146604/) Babies are not born with the mites but acquire them from the people they live with.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites)
Genetic analysis shows that the mites are more diverse than their two species names suggest. The *D. brevis* clade is geographically structured, with the greatest diversity between geographically distinct human populations, and multiple lineages of *D. brevis* can be present even on a single person.[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4146604/)
## Demodex and rosacea
The relationship between Demodex and rosacea, a chronic inflammatory skin condition, has long been debated.[6](https://www.sciencedirect.com/science/article/pii/S0190962217304292) A 2017 systematic review and meta-analysis of 23 case-control studies including 1513 patients with rosacea found that patients with rosacea were significantly more likely to be infested than control patients (odds ratio 9.039; 95% CI 4.827–16.925) and had significantly higher mite density (standardized mean difference 1.617; 95% CI 1.090–2.145). Both erythematotelangiectatic and papulopustular rosacea showed higher density than healthy controls, with papulopustular rosacea tending to be higher.[6](https://www.sciencedirect.com/science/article/pii/S0190962217304292) Elevated density has also been found in rosacea patients compared with patients with discoid lupus erythematosus, acne, and other facial dermatoses.[6](https://www.sciencedirect.com/science/article/pii/S0190962217304292) • [13](https://onlinelibrary.wiley.com/doi/10.1111/j.1610-0387.2010.07513.x/full)
Underlying causality remains unresolved. An epidemiological analysis applying Hill's criteria for causation found that the evidence fails to support a causative role of Demodex in the initiation of rosacea, on grounds including the strength, specificity, and temporality of the association; applying Rothman's sufficient cause model, the mites can be regarded as a non-necessary, non-sufficient causal factor for certain forms of rosacea.[1](https://pubmed.ncbi.nlm.nih.gov/25666117/) The meta-analysis authors likewise noted that case-control data cannot demonstrate a cause-and-effect relationship, while the association suggests the mites may play a pathogenic role.[6](https://www.sciencedirect.com/science/article/pii/S0190962217304292) Indirect evidence includes abnormally elevated mite numbers in rosacea patients measured by non-invasive skin-detecting techniques, increased cytokine levels such as IL-10, IL-8, and IL-12p70 in human sebocytes after Demodex challenge, and the effectiveness of acaricides in rosacea therapy.[10](https://pubmed.ncbi.nlm.nih.gov/37848012/) One proposed mechanism is that rosacea may be fundamentally a bacterial disease resulting from over-proliferation of the mites, with inflammation driven by bacteria associated with them.[14](https://pubmed.ncbi.nlm.nih.gov/22933353/) • [15](https://www.rosacea.org/patients/causes-of-rosacea/demodex-mites-and-microbes)
## Demodicosis and ocular disease
Demodicosis, the symptomatic overgrowth of the mites, is relatively rare despite how common the mites are.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites) It is more likely in people receiving immunosuppressants or chemotherapy, those with immunodeficiency diseases such as HIV and AIDS, people with other skin conditions such as rosacea, and users of itch-relieving creams such as hydrocortisone on the face.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites) Because mites are found on both affected and healthy skin, diagnosis requires compatible clinical manifestations together with a high mite density, above 5 per cm².[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC5383737/) A proposed classification of primary demodicosis includes spinulate demodicosis (pityriasis folliculorum), papulopustular or nodulocystic demodicosis, ocular demodicosis causing chronic blepharitis, chalazia, or keratoconjunctivitis, and auricular demodicosis.[11](https://onlinelibrary.wiley.com/doi/10.1111/bjd.12850/full)
**Demodex blepharitis** is the main ocular manifestation. Both human species inhabit the human eyelid, and the condition is estimated to affect about 58% of eye care patients, roughly 25 million US adults.[16](https://pmc.ncbi.nlm.nih.gov/articles/PMC11311291/) • [17](https://www.accessdata.fda.gov/drugsatfda_docs/nda/2023/217603Orig1s000RiskR.pdf) In the clinical trials supporting drug approval, eligible adults had more than 10 upper-eyelid lashes with collarettes (Cuffs of flaky debris around eyelash roots), at least mild eyelid-margin erythema, and a combined Demodex density of at least 1.5 mites per lash.[8](https://www.fda.gov/drugs/drug-trials-snapshots/drug-trials-snapshots-xdemvy)
## Treatment
Treatment is needed only when mites multiply out of control and cause symptoms.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites) For demodicosis, options include creams, gels, lotions, or washes containing acaricides such as benzyl benzoate, [crotamiton](https://www.edgepedia.org/crotamiton), ivermectin, metronidazole, permethrin, salicylic acid, selenium sulfide, and sulfur products.[3](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites) For Demodex blepharitis, off-label agents including oral ivermectin, metronidazole, and tea tree oil products have been used, but clinical trial data supporting their efficacy and safety in this condition are lacking; intense pulsed light has been shown to reduce mite density over up to 12 weeks of therapy.[18](https://www.aoa.org/AOA/Documents/Advocacy/HPI/Treatment%20Options%20Blepharitis%202025.pdf)
**Lotilaner ophthalmic solution 0.25%** (XDEMVY, Tarsus Pharmaceuticals) became the first FDA-approved treatment for Demodex blepharitis, approved on July 24, 2023 on the basis of two clinical trials of 833 patients.[8](https://www.fda.gov/drugs/drug-trials-snapshots/drug-trials-snapshots-xdemvy) • [16](https://pmc.ncbi.nlm.nih.gov/articles/PMC11311291/) The drug is an isoxazoline, dosed as one drop in each eye twice daily, approximately 12 hours apart, for 6 weeks.[8](https://www.fda.gov/drugs/drug-trials-snapshots/drug-trials-snapshots-xdemvy) • [19](https://www.accessdata.fda.gov/drugsatfda_docs/nda/2023/217603Orig1s000ClinPharmR.pdf) Before these trials, lotilaner had not been used in humans; oral lotilaner was already approved for flea and tick treatment in dogs (2018) and cats (2021).[16](https://pmc.ncbi.nlm.nih.gov/articles/PMC11311291/) • [17](https://www.accessdata.fda.gov/drugsatfda_docs/nda/2023/217603Orig1s000RiskR.pdf) A 2024 meta-analysis of randomized controlled trials of lotilaner for Demodex blepharitis concluded that its approval represents a significant treatment option, while calling for further research and long-term follow-up.[20](https://pubmed.ncbi.nlm.nih.gov/38514290/) A consensus panel of the Demodex Expert Panel on Treatment and Eyelid Health (DEPTH) agreed in 2024 that blepharoexfoliation can supplement, but should be paired with, lotilaner ophthalmic solution 0.25% to eradicate mites in the eyelid; the panel did not reach consensus on how tea tree oil-based products should be used in the current treatment landscape.[21](https://pmc.ncbi.nlm.nih.gov/articles/PMC12183565/)
## References
1. [Are Demodex mites principal, conspirator, accomplice, witness or bystander in the cause of rosacea? PubMed](https://pubmed.ncbi.nlm.nih.gov/25666117/)
2. [Human Permanent Ectoparasites; Recent Advances on Biology and Clinical Significance of Demodex Mites, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC5522688/)
3. [Demodex (Face Mites): Folliculorum, Brevis & Treatment, Cleveland Clinic](https://my.clevelandclinic.org/health/diseases/22775-demodex-face-mites)
4. [Under the lash: Demodex mites in human diseases, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC2906820/)
5. [Ubiquity and Diversity of Human-Associated Demodex Mites, PLOS One, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4146604/)
6. [Role of Demodex mite infestation in rosacea: A systematic review and meta-analysis, Journal of the American Academy of Dermatology](https://www.sciencedirect.com/science/article/pii/S0190962217304292)
7. [Demodex Mite Density Determinations by Standardized Skin Surface Biopsy and Direct Microscopic Examination, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC5383737/)
8. [Drug Trials Snapshots: XDEMVY, FDA](https://www.fda.gov/drugs/drug-trials-snapshots/drug-trials-snapshots-xdemvy)
9. [Meet Your Skin's Secret Inhabitants: The Truth About The Skin Mites Living On Your Face, Marie Claire](https://www.marieclaire.co.uk/beauty/skincare/demodex-skin-mites)
10. [Evidence for the Clinical Association between Demodex and Rosacea: A Review, PubMed](https://pubmed.ncbi.nlm.nih.gov/37848012/)
11. [Human demodicosis: revisit and a proposed classification, British Journal of Dermatology](https://onlinelibrary.wiley.com/doi/10.1111/bjd.12850/full)
12. [Theoretical and Applied Approaches in Health Sciences (Demodex chapter)](https://www.duvaryayinlari.com/Webkontrol/IcerikYonetimi/Dosyalar/theoretical-and-applied-approaches-in-health-sciences_icerik_g4619_WaGO9V7S.pdf)
13. [The potential role of microorganisms in the development of rosacea, JDDG](https://onlinelibrary.wiley.com/doi/10.1111/j.1610-0387.2010.07513.x/full)
14. [Potential role of Demodex mites and bacteria in the induction of rosacea, PubMed](https://pubmed.ncbi.nlm.nih.gov/22933353/)
15. [Causes of Rosacea: Demodex Mites & Microbes, Rosacea.org](https://www.rosacea.org/patients/causes-of-rosacea/demodex-mites-and-microbes)
16. [Lotilaner Ophthalmic Solution, 0.25%, for the Treatment of Demodex Blepharitis, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC11311291/)
17. [FDA NDA Review, Risk Assessment (lotilaner ophthalmic solution 0.25%)](https://www.accessdata.fda.gov/drugsatfda_docs/nda/2023/217603Orig1s000RiskR.pdf)
18. [Treatment Options: Blepharitis, American Optometric Association](https://www.aoa.org/AOA/Documents/Advocacy/HPI/Treatment%20Options%20Blepharitis%202025.pdf)
19. [FDA NDA Clinical Pharmacology Review (lotilaner ophthalmic solution 0.25%)](https://www.accessdata.fda.gov/drugsatfda_docs/nda/2023/217603Orig1s000ClinPharmR.pdf)
20. [Efficacy and Safety of Lotilaner Ophthalmic Solution 0.25% for the Treatment of Demodex Blepharitis: A Meta-Analysis of Randomized Controlled Trials, PubMed](https://pubmed.ncbi.nlm.nih.gov/38514290/)
21. [The DEPTH Consensus Regarding the Preferred Treatment for Demodex Blepharitis, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC12183565/)
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*Topic: Encyclopedia › Life and health › Animals › Invertebrates › Arthropods › Arachnids › Mites and ticks › Parasitic and pest mites › Mites affecting humans › Demodex mites of humans*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026; Oct 25, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license