The effects of long‐pulsed alexandrite laser therapy on facial redness and skin microbiota compositions in rosacea: A prospective, multicentre, single‐arm clinical trial

Background Rosacea is a chronic skin disorder characterised by abnormal neurovasculature and inflammation in the central region of the face. The efficacy of pulsed‐dye laser and intense pulsed light treatments for rosacea have been demonstrated in several clinical trials. However, there is currently no research on the efficacy of long‐pulsed alexandrite laser (LPAL) therapy alone for rosacea‐related facial redness and its effect on skin microbiota. Aim To evaluate the efficacy of LPAL therapy on facial redness in rosacea and assess changes in skin microbiota composition. Methods Subjects with rosacea (n = 21, mean age: 39.2 ± 11.3 years) were recruited from two medical institutions and received monthly LPAL treatments (Clarity II™, Lutronic Corp.) for 3 months. At each visit, clinical photographs were taken, and erythema was measured using a spectrometer. At the initial and final visits, the Dermatology Life Quality Index (DLQI) and Skin Sensitivity Questionnaire (SSQ) were evaluated. Skin swabs were obtained at the initial and final visit, and facial microbiome composition was analysed using 16S rRNA amplicon sequencing. Results After three LPAL treatment sessions, the average facial erythema index, measured using Mexameter® decreased significantly from 360.0 ± 96.7 at baseline to 312.0 ± 94.5 at the final visit (p