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What is Demodex infestation?

 

A Demodex infestation is an infection with the tiny or microscopic (0.15-0.4mm) mites of the subfamily Demodex, of which two members infest humans: Demodex folliculorum and Demodex brevis. Demodex folliculorum lives in small hair follicles and is often found in eyelashes. Since it is commonly found it eyelashes, it was given the name “eyelash mite”. Demodex brevis lives in the oil (sebaceous and meibomian) glands that are connected to the small hair follicles, especially on the trunk of the body. (Citation: 1) Both mites feed on human cells: skin cells for Demodex folliculorum and gland cells for Demodex brevis. (Citation: 2)

Demodex mites were discovered over 150 years ago and were considered initially as commensals due to their symbiotic (asymptomatic) presence, but they are now often considered parasites that contribute eye and skin conditions. (Citation: 4) In animals, Demodex mites can contribute to mange. (Citation: 1)

 

How common are Demodex infestations?

 

Demodex infestations are widespread. It affects people all over the world from every socio-economic background with an estimated prevalence rate of 23-100%. (Citations: 3, 4) It is more common in females (for Demodex folliculorum), and the prevalence rate increases with age, although infestations can also be more common in immunocompromised children. (Citation: 5)

 

Is Demodex infestation contagious?

 

Demodex mites can be transmitted through direct contact with infected skin areas or through contact with personal items of that person including clothing, bedding, towels and combs. (Citation: 4) The 14-day life cycle of Demodex has four stages: egg, larva, nymph and adult. The Demodex mite easily lives for several weeks during its life cycle. (Citation: 3)

 

What are signs and symptoms of Demodex infestations?

 

Demodex infestations are often asymptomatic. If there are symptoms, they can usually be found on the eyelids and the skin on the face. The two most common symptomatic conditions are Demodex dermatitis (or demodicosis) and blepharitis (inflammation of the eyelids). (Citation: 3, 6, 7, 8)

Demodicosis is a scabies-like dermatitis that is sometimes called mange. (Citation: 9) Demodicosis is usually found on the face with scaling, red, sensitive and itchy skin patches. There might also be spots, pimples, infected hair follicles, eczema and pigmentation. The demodicosis is often found together with blepharitis: irritated eyes with itchy, scaling eyelids. There might also be a loss of eyelashes (madarosis), conjunctivitis, decreased eyesight and thickening of the eyelids. (Citation: 2) Others also report cylindrical dandruff around the eyelashes. (Citation: 10)

 

How to diagnose Demodicosis and Demodex blepharitis?

 

For an official diagnosis of demodicosis, a clinical examination or even finding Demodex mites on the surface of the skin is not sufficient. A microscopic examination of skin scrapings and a skin surface biopsy is needed to determine the density of the mites and extrafollicular location where they are found. (Citation: 3, 11) If the density of the Demodex mites is more than 5/cm2, then demodicosis can be “officially” diagnosed. Similarly, while a blepharitis (of any cause) can be diagnosed clinically, for a Demodex blepharitis several Demodex mites need to be found. This can be done through examining epilated eyelashes. Special counting methods have been developed for diagnosingDemodex blepharitis. (Citation: 9) Sometimes the mites can be confused with the scabies mites. (Citation: 12)

 

What Is the treatment for a Demodex infestation?

Treatment of Demodex infestations is a combination of eradicating the mites and symptomatic treatment of the effects of the mites.

Mites can be eradicated with topical preparations (crotamiton cream, permethrin cream, metronidazole, lindane) or oral metronidazole. (Citation: 13) In severe infections as well as patients with a weakened immune system oral ivermectin can be considered. For Demodex blepharitis, Tea Tree oil has been mentioned as an effective treatment for many people. (Citation: 2, 3, 9)

 

What are complications of Demodex infestations?

Recent research shows that there is an association between acne vulgaris and Demodex infestations. The authors advise considering treatment for Demodicosis if regular acne vulgaris treatments are not effective. (Citation: 14) There are also indications of a relation between Demodex and the associated bacteria found with Rosacea (facial dermatitis with enlarged blood vessels that give a flushed appearance to cheeks and nose). (Citation: 15, 16, 17)

 

What are preventive measures against Demodex?

 

Human Demodex mites survive inside of the human hair follicles, and many people say cause no problems in most when they are kept under control. To prevent excessive proliferation of the Demodex mite population on the face and skin, those affected should clean the irritated area two times per day with a non-soap cleanser, and periodic exfoliation should be done to remove dead skin cells. Oil-based cleansers and greasy make-up should be avoided. When there are clinical signs, the mites should be (temporarily) eradicated or reduced using the treatment protocols mentioned. (Citation: 3)

References
  1. Elston and Elston. Demodex Mites. Clinical Dermatology 2014 Nov-Dec; 32(6): 739-43. doi: 10.1016/j.clindermatol.2014.02.012. Epub 2014 Feb 28. Weblink (abstract): https://www.ncbi.nlm.nih.gov/pubmed/25441466
  2. DermNet New Zealand. Accessed online 6th October 2017. Weblink: https://www.dermnetnz.org/topics/demodex
  3. Rather and Hassan. Human Demodex mite: The versatile mite of dermatological importance. Indian Journal of Dermatology 2014 Jan-Feb; 59(1): 60-66. doi: 4103/0019-5154.123498. Weblink: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3884930/  (including pictures of life cycle, clinical presentation)
  4. MedScape. Accessed online 6th October 2017. Weblink: http://emedicine.medscape.com/article/1203895-overview . Tab: Epidemiology.
  5. Rusiecka-Ziółkowska and others. Demodex – an old pathogen or a new one? Advances in Clinical and Experimental Medicine 2014 March-April; 23(2): 295-8. Weblink: Abstract: https://www.ncbi.nlm.nih.gov/pubmed/24913122 and Full PDF (including Demodex picture): http://www.advances.umed.wroc.pl/pdf/2014/23/2/295.pdf
  6. MedScape. Accessed online 6th October 2017. Weblink: http://emedicine.medscape.com/article/1203895-overview
  7. Lindsley K and others. Interventions for chronic blepharitis. Cochrane Database of Systematic Reviews 2012, Issue 5. Art. No.: CD005556. DOI: 10.1002/14651858.CD005556.pub2. Weblink: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD005556.pub2/abstract
  8. Mayo Clinic. Accessed online 6th October 2017. Weblink: http://www.mayoclinic.org/diseases-conditions/blepharitis/basics/causes/con-20024605
  9. Merck Manual Professional Version. Accessed online 6th October 2017. Weblink: http://www.merckmanuals.com/professional/injuries-poisoning/bites-and-stings/mite-bites
  10. Ocular Surface Research & Education Foundation. Accessed online 6th October 2017. Weblink (including pictures): http://www.osref.org/medical-education-materials/demodex-blepharitis-diagnosis-and-treatment.aspx
  11. DermNet New Zealand. Accessed online 6th October 2017. Weblink: https://www.dermnetnz.org/topics/demodicosis-pathology (includes pictures).
  12. Centers for Disease Control and Prevention. Accessed online 6th October 2017. Weblink: https://www.cdc.gov/dpdx/scabies/index.html . Tab: Image gallery (scroll to the end to see Demodex)
  13. Bikowski JB and Del Rosso JQ. Demodex Dermatitis – A retrospective analysis of clinical diagnosis and successful treatment with topical crotamiton. The Journal of Clinical and Aesthetic Dermatology. 2009 January; 2(1): 20-25. Weblink: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2958185/
  14. Zhao and others. A meta-analysis of association between acne vulgaris and Demodex infestation. Journal of Zhejiang University SCIENCE B. 2012 March; 13(3): 192-202. doi: 1631/jzus.B1100285 . Weblink: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3296070/
  15. Jarmuda and others. Potential role of Demodex mites and bacteria in the induction of rosacea. Journal of Medical Microbiology 2012 November 01; 61: 1504-1510. doi: 10.1099/jmm.0.048090-0. Weblink: http://jmm.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.048090-0
  16. National Health Service United Kingdom. Accessed online 6th October 2017. Weblink: http://www.nhs.uk/Conditions/Rosacea/Pages/Causes.aspx
  17. van Zuuren and others. Interventions for rosacea. Cochrane Database of Systematic Reviews 2015, Issue 4. Art. No.: CD003262. DOI: 10.1002/14651858.CD003262.pub5. Weblink: http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD003262.pub5/abstract

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