The goal of this observational study is to investigate whether the density of Demodex mites is higher in psoriasis patients treated with biologic agents compared to treatment-naive or topically treated patients. The main question[s]it aims to answer are:

• Are Demodex mites higher in psoriasis patients treated with biologic agents?
• In which localization and with what intensity was demodicosis most common?

Participants will be assessed using standardized skin surface biopsy technique in four localization on their face .

Researchers will compare demodex intensity per cm² to see if the biologic treatments effects demodex intensity on psoriasis patients.

This study employes a cross-sectional design to compare the density of Demodex mites in psoriasis patients receiving biologic therapy and those who had not yet initiated any treatment or were using topical medications only. The study is going to be conducted at Istanbul Medeniyet University Department of Dermatology between July 2023-August 2023. Ethics approval was obtained from Istanbul Medeniyet University Local Ethics Commitee (decision number:2022/0341).

A standardized form will be used to collect demographic information, and details regarding smoking and alcohol habits. Additional information regarding their treatment regimens will be recorded. Furthermore, patients will be evaluated for the presence of acne, rosacea, perioral dermatitis, seborrheic dermatitis, folliculitis, blepharitis, or pityriasis folicullorum, as these conditions have been associated with an increased Dd.

The standardized skin surface biopsy (SSSB) technique is going to be utilized to assess demodicosis. This technique will be applied in four facial localizations, including the forehead, cheeks, and nose. The surface biopsy procedure will be performed as follows: one cm² area will be marked on a glass slide using a fine ruler. The designated skin area for sampling will be gently swabbed with a dry gauze pad to create mild irritation. Subsequently, one drop of cyanoacrylate adhesive will be applied to the marked area on the glass slide. The glass slide will be carefully pressed onto the skin, allowing the adhesive to adhere. After approximately one minute, the glass slide will be gently lifted. The sampled area on the glass slide will be examined under x10 and x40 magnification. Immersion oil will be applied to enhance visualization and determine the number of Demodex parasites within the marked area. An increased Demodicosis will be defined as the presence of five or more Demodex parasites per square centimeter of skin.

Statistical analysis will be performed using Statistical Package for the Social Sciences [SPSS] v.17. Descriptive statistics will be calculated for relevant variables, including means, standard deviations, and frequencies. The independent samples t-test will be utilized to compare the Demodex densities, and the Chi-Square test will be used to compare the presence of demodicidosis between the two groups. P-values less than 0.05 will be considered statistically significant.

Inclusion Criteria:

• pathologically or clinically diagnosed psoriasis patients receiving biologic therapy or topical therapy or treatment naive.

Exclusion Criteria:

• systemic therapy other then biologic agents including methotrexate, asitretin, cyclosporin etc.

psoriasis patients aged between 18 and 70 which are diagnosed pathologically or clinically receiving biologic therapy or topical therapy .