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Demodex Density Count - What are the Numbers?

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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. 

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 significan tly reduced Dd in facial skin with one session." [10]

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

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

[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

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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 by 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:

“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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