Demodex Mite Density Increases in Psoriasis Patients Treated with Biologic Therapy

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These data allow for a basis for additional research and possible interventions to address psoriasis patients’ demodicosis risk.

Individuals with psoriasis and treated with biologics have higher Demodex density and demodicosis prevalence, according to new findings, suggesting that biologics may result in Demodex density increases by blocking certain cytokines.1

These findings represented the conclusion of a recent cross-sectional study, led by Hasan Aksoy, of the department of dermatology at Istanbul Medeniyet University Prof. Dr. Suleyman Yalcin City Hospital in Istanbul, assessing the possibility of Demodex mites density being higher in patients with psoriasis treated with biologics versus treatment-naive patients or those treated topically.

Aksoy et al. noted that In recent years, the treatment of individuals with psoriasis has relied heavily on biologics which are designed to aim at specific elements of patients’ immune system.2 While there are data suggesting increased Demodex density (Dd) for those with different immunosuppressive conditions, the relationship between antipsoriatic biologics and Demodex mites had been somewhat unclear.

“Our study aims to investigate whether the density of Demodex mites on the face is higher in psoriasis patients treated with biological agents than in treatment-naive or topically treated psoriasis patients,” Aksoy and colleagues wrote. “By assessing the impact of biological therapies on Dd, we aim to gain insights into the potential influence of these treatments on skin immunity.”

Background and Methods

The investigators utilized a cross-sectional study design with the overall goal of comparing the Demodex mite density in patients with psoriasis undergoing biologic treatment with psoriasis patients without any treatment or implementing only topical medication options for their skin condition. The research team’s work spanned from May 2023 - June 2023.

The team utilized a standardized form to gather study participants’ demographic information, habits related to cigarette-smoking and alcohol, and details of treatment for psoriasis. Those participating in the study were also evaluated for conditions such as rosacea, perioral dermatitis, blepharitis, seborrheic dermatitis, acne, folliculitis, or pityriasis folliculorum, given the conditions’ known links to increased Demodex mite density.

The skin surface biopsy technique (SSSB) technique was implemented by the investigators to assess density, with the technique involving the distinct facial regions of the forehead, cheeks, and nose. The SSSB procedure involved the marking of a 1 cm area on a single glass slide, with the team swabbing patients’ skin using a dry gauze pad, then applying cyanoacrylate adhesive and looking at their given sample under ×10 and ×40 magnification using immersion oil.

The research team defined the presence of Demodex mites as the presence of 5 or more such parasites per square centimeter of subjects’ skin. The team also carried out their statistical analyses by comparing density and demodicosis prevalence between both treatment cohorts.


Overall, the investigators found that the density of subjects’ Demodex mites suggested a major increase among those in the arm undergoing biologic treatment compared to those in the control arm, notably on subjects’ left cheeks (8.15 compared to 0.24/cm2; P = .002), right cheeks (7.29 compared to 0.12/cm2; P = .001), and general face area (average of all four regions: 5.50 compared to 0.80/cm2; P = .001).

The research team also noted that prevalence of demodicosis had been observed to be much higher within subjects featured in the biologic arm on their right cheeks (41.2% compared to 0%; P < 0.001), foreheads (35.3% compared to 12.1%; P = .043), and left cheeks (44.1% compared to 0%; P < .001). They also found that the frequency of cases shown to have demodicosis at 1 area minimum had been far greater among those in the biologic cohort versus those in the control cohort (61.8% compared to 15.2%; P < .001).

“Our study contributes to the growing body of evidence linking immunosuppression and Demodex colonization,” they wrote. “By shedding light on the association between biologic therapy and Demodex density in psoriasis patients, we provide a basis for further research and potential interventions to minimize the risk of demodicosis in immunosuppressed individuals.”


  1. Aksoy, H., Altıntaş Kakşi, S., Gönüllü, Ö., Aslan Kayıran, M. and Erdemir, V.A. (2024), Biologic therapy increases Demodex density in psoriasis patients. Int J Dermatol.
  2. Armstrong AW, Read C. Pathophysiology, clinical presentation, and treatment of psoriasis: a review. JAMA. 2020; 323: 1945–1960.