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Demodex Density Count - What are the Numbers?


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Demodex Density Counts Higher in Rosaceans

In many papers on rosacea, demodex density counts are higher than in the normal population. Below are reports about this subject, but the consensus is that five or more demodex mites per square centimeter is when there is an issue with demodectic rosacea. The normal count is 1 to 2 demodex mites per square centimeter for non rosacea subjects or in normal human subjects.  

One report says, "Studies have found that people suffering from rosacea tend to have more Demodex mites. Instead of 1 or 2 per square centimetre of skin, the number rises to 10 to 20."
These Microscopic Mites Live on Your Face, by Lucy Jones, May 8, 2015, BBC Earth

"The mean mite count was 49.8 (range 2 to 158) in patients with rosacea and 10.8 (range up to 97) in control subjects (p < 0.001); the highest density of mites was found on the cheeks. A statistically significant increase in mites was found in all subgroups of rosacea, being most marked in those with steroid-induced rosacea." [1]

"The mean mite density was 2.03 mites/visual field in the rosacea group (range 0-5, SD = 1.2) and 0.16 mites/visual field (range 0-2, SD = 0.52) in the control group." [2]

"A mean density of 0.7 Demodex folliculorum/cm2 was found in controls, 98% of whom had less than five Demodex/cm2. When all clinical types of rosacea were considered collectively, the density of Demodex was significantly higher in patients with rosacea than in controls (mean = 10.8/cm2; P < 0.001). When the various clinical types of rosacea were considered separately, Demodex density was statistically significantly higher than in controls only in the PPR patients (mean = 12.8/cm2; P < 0.001)." [3]

"The results of our study revealed that DME [direct microscopic examination] is a more sensitive method for detecting Demodex than SSSB [Standardized skin surface biopsy], especially in patients with diffuse pattern and suspected rosacea type. Further research is needed to confirm this finding." [4]

"Every human being carries a colony of 1000 to 2000 Demodex mites." [5]

"More than five mites per cm2 are assumed a positive diagnosis of demodicosis. The validity of this optimal threshold is rather artificial and weakly evidence-based." [5]

"SSSB and DME were used to measure Demodex mites density (Dd). For SSSB, a standard area of 1 cm2 was drawn on a slide with a waterproof pen. A drop of cyanoacrylic adhesive was then placed on the other side of the slide and the adhesive-bearing surface was applied to the skin for one minute. After allowing the adhesive to dry, the slide was removed gently with surface skin, clarified with one to two drops of immersion oil, and covered with a cover slip. For DME, a 1 cm2 sized affected skin area was squeezed using a comedo extractor. The sample obtained was transferred to a 10% potassium hydroxide drop and covered with a cover slip. Samples obtained using both methods were studied under an optical microscope (×40, ×100)." [6]

"Patients with rosacea had significantly higher prevalence and degrees of Demodex mite infestation than did control patients." [7]

"The diagnosis of demodicosis was made when compatible clinical manifestations of demodicosis was combined with a high Dd (>5D/cm2) by SSSB, or DME." [6]

"High numbers of Demodex induced pro-inflammatory cytokine secretion whereas lower numbers did not. Demodex mites have the capacity to modulate the TLR signalling pathway of an immortalised human sebocyte line. Mites have the capacity to secrete bioactive molecules that affect the immune reactivity of sebocytes. Increasing mite numbers influenced IL8 secretion by these cells." [8]

"In the case of cutaneous demodicosis the presence of 5 or more Demodex on 1 cm2 will significantly increase the risk of cutaneous demodicosis." [9]

There is evidence that decreasing the mite count improves rosacea

"The present study shows that PDL significantly reduced Dd in facial skin with one session." [10]

"To overcome this limitation we evaluated a new quantitative method of evaluating the viability of Demodex mites by using scattered light intensity (SLI)." [11]

Demodex Brevis Higher Count Than Demodex Folliculorum in Cylindrical Dandruff Patients

"Demodex infestation rates were significantly higher in the rosacea group than acne vulgaris and seborrheic dermatitis groups and controls (p=0.001; p=0.024; p=0.001, respectively)." [14]

"Demodex mites may be found on normal skin with a density of <5 mites/cm2. A diagnosis of demodicosis or Demodex infestation is considered when clinical signs/symptoms appear and when more than 5 mites/cm2 are present or when they penetrate into the dermis." [19]

Increased Blood Glucose Level Correlates Increase in Demodex Density Count

Do the Numbers Matter?

The answer to that question according to one report [12],  if you use a skin scraping with a light microscope, is no, which the report says, "The severity of the condition does not depend on the quantitative load of the mites in the scrape." Other reports say otherwise. 

However when using a 'Confocal laser scanning in vivo microscopy',  the answer is yes, which this same report concludes, "Confocal laser scanning in vivo microscopy is an effective diagnostic method to detect Demodex mites that does not require preliminary preparation for analysis and allows detecting Demodex mites at the level of the spiky epidermis layer, which is not accessible for scarification, to identify the species belonging to the size of Demodex mites (from 100 up to 200 μm - Demodex brevis, 200 to 400 μm – Demodex folliculorum)." [12]

"Comparing the results obtained by light microscopy and confocal laser scanning in vivo microscopy in patients with rosacea and healthy people, in more cases Demodex mites are detected by confocal laser scanning in vivo microscopy, whereas scrape in these patients were negative."  [12]

"As a result of the study, we found that it is difficult to detect the mite by light microscopy of scrape per 1 cm2 of skin." [12]

For more information on how to quantify demodex density go to the subheading, Quantification and Methods for Demodex Density Counts in this article.

One study on comparing Standardized skin surface biopsy (SSSB) with Superficial Needle-Scraping (SNS) concluded that "that SNS is a simple and convenient method for assessing Demodex density of pustules in PPR and can be a useful alternative or addition to SSSB for evaluation of Demodex-associated facial papulopustular eruptions." [13]

Tools to Detect or Quantify Demodex Density Counts

confocal-laser-scanning-microscope_thumb
Cellophane Tape Method [20]

CLSM [Confocal laser scanning in vivo microscopy] [16]

DME [direct microscopic examination] 

Dermoscopy [17]

Microscope (simple)

RCM [reflectance confocal microscopy] [18]

Skin Scraping [potassium hydroxide preparation of skin scrapings]

SLI [scattered light intensity]

SSSB [standardized skin surface biopsy

SNS [superficial needle-scraping

Supereyes Macro Lens-Disposable Dermatoscope

Supereyes Smartphone Microscope Camera Adapter

Thumbnail-squeezing method

CLSM - did your dermatologist use this device to quantify your demodex density count? According to a Russian study [12], the CLSM in vivo method is the best method of quantifying demodex density counts which needs to be validated by comparing the other tools used. Another paper in Thailand states that SSSB has been 'considered to be the gold standard technique' but after careful investigation that the Skin Scraping technique is just as valid. [15] The paper by Karabay et al shows phots of using SSSB. [19]

See also, Methods for Quantifying Demodex Mites.

End Notes

[1] J Am Acad Dermatol. 1993 Mar;28(3):443-8.
The Demodex mite population in rosacea.
Bonnar E, Eustace P, Powell FC.

[2] J Eur Acad Dermatol Venereol. 2001 Sep;15(5):441-4.
Increased density of Demodex folliculorum and evidence of delayed hypersensitivity reaction in subjects with papulopustular rosacea.
Georgala S, Katoulis AC, Kylafis GD, Koumantaki-Mathioudaki E, Georgala C, Aroni K.

[3] Br J Dermatol. 1993 Jun;128(6):650-9.
Density of Demodex folliculorum in rosacea: a case-control study using standardized skin-surface biopsy.
Forton F, Seys B.

[4] Ann Dermatol. 2017 Apr;29(2):137-142
Demodex Mite Density Determinations by Standardized Skin Surface Biopsy and Direct Microscopic Examination and Their Relations with Clinical Types and Distribution Patterns.
Yun CH, Yun JH, Baek JO, Roh JY, Lee JR

[5] Iran J Parasitol. 2017 Jan-Mar; 12(1): 12–21.
PMCID: PMC5522688
Human Permanent Ectoparasites; Recent Advances on Biology and Clinical Significance of Demodex Mites: Narrative Review Article
Dorota LITWIN,  WenChieh CHEN, Ewa DZIKA, and Joanna KORYCIŃSKA

Another paper concluded:
"Determination of five or more parasites in 1 cm2 area was considered as positive."
Medicina (Kaunas). 2020 Mar; 56(3): 107.
Pre-Treatment and Post-Treatment Demodex Densities in Patients under Immunosuppressive Treatments
Hacer Keles, Esra Pancar Yuksel, Fatma Aydin, and Nilgun Senturk

[6] Ann Dermatol. 2017 Apr; 29(2): 137–142.
Published online 2017 Mar 24. doi:  10.5021/ad.2017.29.2.137
PMCID: PMC5383737
Demodex Mite Density Determinations by Standardized Skin Surface Biopsy and Direct Microscopic Examination and Their Relations with Clinical Types and Distribution Patterns
Chul Hyun Yun, Jeong Hwan Yun, Jin Ok Baek, Joo Young Roh, and Jong Rok Lee

[7] "Twenty-three case-control studies included 1513 patients with rosacea. Compared with the control patients, patients with rosacea were more likely to be infested by Demodex mites [odds ratio, 9.039; 95% confidence interval (CI), 4.827-16.925] and had significantly higher Demodex density (SMD, 1.617; 95% CI, 1.090-2.145). Both erythematotelangiectatic rosacea (SMD, 2.686; 95% CI, 1.256-4.116) and papulopustular rosacea (SMD, 2.804; 95% CI, 1.464-4.145) had significantly higher Demodex density than did healthy control patients."

JAAD, September 2017 Volume 77, Issue 3, Pages 441–447.e6
Role of Demodex mite infestation in rosacea: A systematic review and meta-analysis
Yin-Shuo Chang, MD, Yu-Chen Huang, MD

[8] Demodex mites modulate sebocyte immune reaction: Possible role in the pathogenesis of rosacea.
Br J Dermatol. 2018 Mar 12;:
Lacey N, Russell-Hallinan A, Zouboulis CC, Powell FC

[9] Arch Med Sci. 2018 Mar; 14(2): 353–356.
Published online 2016 Jun 17. doi:  10.5114/aoms.2016.60663; PMCID: PMC5868666
The impact of age, sex, blepharitis, rosacea and rheumatoid arthritis on Demodex mite infection
Aleksandra Sędzikowska, Maciej Osęka, and Piotr Skopiński

[10] J Cosmet Laser Ther. 2018 Jun 08;:1-4
The rapid effect of pulsed dye laser on demodex density of facial skin.
Ertaş R, Yaman O, Akkuş MR, Özlü E, Avcı A, Ulaş Y, Ozyurt K, Atasoy M

[11] Exp Appl Acarol. 2019 Apr 19;:
Evaluation of Demodex mite viability using motility and scattered light intensity.

Gatault S, Foley R, Shiels L, Powell FC

[12] Dermatol Reports. 2019 Jan 23; 11(1): 7675.
Clinical picture, diagnosis and treatment of rosacea, complicated by Demodex mites
Alexey Kubanov, Yuliya Gallyamova, and Anzhela Kravchenko

[13] J Cosmet Dermatol. 2019 Jul 25. doi: 10.1111/jocd.13082. [Epub ahead of print]
A new superficial needle-scraping method for assessing Demodex density in papulopustular rosacea.
Huang HP, Hsu CK, Lee JY.

[14] An Bras Dermatol. 2020 Feb 12;:
Demodex folliculorum infestations in common facial dermatoses: acne vulgaris, rosacea, seborrheic dermatitis.

Aktaş Karabay E, Aksu Çerman A

[15] Indian J Dermatol Venereol Leprol. 2016 Sep-Oct;82(5):519-22. doi: 10.4103/0378-6323.174423.
Skin scrapings versus standardized skin surface biopsy to detect Demodex mites in patients with facial erythema of uncertain cause - a comparative study.
Bunyaratavej S, Rujitharanawong C, Kasemsarn P, Boonchai W, Muanprasert C, Matthapan L, Leeyaphan C.

[16] Br J Dermatol. 2012 Jun 20. doi: 10.1111/j.1365-2133.2012.11096.x.
 
Non-invasive in vivo detection and quantification of Demodex mites by confocal laser scanning microscopy.
Sattler EC, Maier T, Hoffmann VS, Hegyi J, Ruzicka T, Berking C.

What is confocal laser scanning microscopy?

[17] Dermatol Pract Concept. 2017 Jan; 7(1): 35–38.
Published online 2017 Jan 31. doi:  10.5826/dpc.0701a06
PMCID: PMC5315038
Usefulness of dermoscopy in the diagnosis and monitoring treatment of demodicidosis
Paula Friedman, Emilia Cohen Sabban, and Horacio Cabo

Int J Dermatol. 2010 Sep;49(9):1018-23.
Dermoscopy as a diagnostic tool in demodicidosis.
Segal R1, Mimouni D, Feuerman H, Pagovitz O, David M.

[18] RCM • Distinguishing rosacea from sensitive skin by reflectance confocal microscopy.
Skin Res Technol. 2014 Feb 13.
Reflectance confocal microscopy vs. standardized skin surface biopsy for measuring the density of Demodex mites.
Turgut Erdemir A, Gurel MS, Koku Aksu AE, Bilgin Karahalli F, Incel P, Kutlu Haytoğlu NS, Falay T.

What is reflectance confocal microscopy?

A paper on RCM states, “In its current form, RCM seems of limited value for noninvasive follow-up of rosacea inclinical practice.”

"RCM enables anti-inflammatory effect monitoring of topical ivermectin by determining mite presence. Quantifying exact mite number, and inflammatory and vascular characteristics is challenging due to device limitations. In its current form, RCM seems of limited value for noninvasive follow-up of rosacea in clinical practice."
J Dermatolog Treat. 2020 Mar 19;:1-9
Value of reflectance confocal microscopy for the monitoring of rosacea during treatment with topical ivermectin.
Logger JGM, Peppelman M, van Erp PEJ, de Jong EMGJ, Nguyen KP, Driessen RJB

[19] An Bras Dermatol. 2020 Mar-Apr; 95(2): 187–193.
Demodex folliculorum infestations in common facial dermatoses: acne vulgaris, rosacea, seborrheic dermatitis
Ezgi Aktaş Karabay and Aslı Aksu Çerman

[20] The cellophane tape method (placing tape on the face to stick to the mites)
Ubiquity and Diversity of Human-Associated Demodex Mites, paragraph 2

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A biopsy is not required to take a demodex density count. All is needed is dermoscopy: 

Scroll down to this article and look for Dermoscopy for more details. What are the numbers of demodex on normal skin compared to those who have demodectic rosacea? They are reports that the numbers are higher in rosacea sufferers who suffer from demodectic rosacea. One report says, "Instead of 1 or 2 per square centimetre of skin, the number rises to 10 to 20." Another report says, "The mean mite count was 49.8 (range 2 to 158) in patients with rosacea and 10.8 (range up to 97) in control subjects (p < 0.001); the highest density of mites was found on the cheeks. A statistically significant increase in mites was found in all subgroups of rosacea, being most marked in those with steroid-induced rosacea."

There are reports in RF of simply taking a cellophane tape scraping of the cheek and examining under a simple microscope you can buy at Amazon and do it yourself, for example this post. 

There is evidence that decreasing the demodex density count improves rosacea.  

Physicians rarely take demodex density counts. In his authoritative book on rosacea, Frank Powell, MD, wrote on the last paragraph of page 82 in his book recommending taking a demodex density count:

“There is no laboratory test or investigation that will confirm the diagnosis of PPR. Specific investigations may be required to rule out similar appearing conditions (many of which will be identified by listening carefully to the patient’s medical history and examining the skin lesions). These include skin swabs for bacterial culture, skin scrapings for the presence of demodex mites, scrapings for fungal KOH and fungal culture, skin biopsy for histologic examination, (and rarely culture) skin surface biopsy for demodex mite quantification, patch tests, photopatch tests, and very rarely systemic workup wih appropriate blood tests and radiological examinations.”

How many dermatologists do you know do such a detailed history and examination? When you were diagnosed with rosacea, did your physician come close to what is mentioned in the above paragraph?

So be sure to read HunkeyMonkey's post on Cheap and easy home test for Demodex

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