This clinical observational study investigates the dose-response relationship between laser energy intensity and skin damage/repair by applying different parameter sets of fractional ablative (CO2) and non-ablative (M22) lasers to the inner forearms of approximately 20 healthy Chinese female volunteers (aged 18-60, Fitzpatrick skin types III-V) in a single-center, self-controlled design. Each participant receives both laser types on contralateral arms, with four distinct energy/density combinations per laser applied to separate test areas, and the dynamic skin responses are evaluated at baseline, immediately post-treatment, and at 30 minutes, 1, 2, 3, 4 hours, 7 days, and 10 days thereafter through clinical assessments (edema, erythema, etc.), standardized photography, high-frequency ultrasound (Dermascan), and objective instrumental measurements of skin color (Chromameter CM26dG), melanin/hemoglobin (Mexameter MX18), and barrier function (TEWL via Vapometer). The collected data will be analyzed using descriptive and comparative statistical methods to characterize the acute injury and recovery profiles, aiming to establish a foundational model for future post-procedure cosmetic intervention research.

Inclusion Criteria:

• Female Chinese study participants aged 18 to 60 years (inclusive).
• Fitzpatrick skin phototypes III, IV, or V.
• Willing to receive non-ablative fractional laser (M22) and ablative fractional laser (CO2) irradiation on the test sites during the study.
• No primary or secondary lesions (such as scars, ulcers, vesicles, tattoos) on the test sites.
• Has not participated in any other studies involving the test area (forearms) in the past 2 months.
• Agrees not to use skin-whitening products on the test area during the study period.
• In good general health at the time of the study.
• Volunteers to participate and signs the informed consent form and photo release authorization.
• Willing to comply with all requirements of the study.

Exclusion Criteria:

• Study participants with skin diseases or skin allergies in the test area.
• Presence of moderate to severe inflammatory skin diseases (e.g., active eczema, acute photosensitive dermatitis, etc.) on the test sites within the past 4 weeks, or those who require treatment with oral or topical corticosteroids or immunosuppressants for skin conditions.
• On the day of the visit, the investigator judges the presence of significant diffuse erythema, desquamation, or exudation in the test area that may significantly affect skin color measurement.
• The investigator assesses that the participant is currently suffering from a stable or progressively worsening disease.
• Participant is planning for pregnancy, is pregnant, or is breastfeeding (applicable to female participants only).
• Participant with immunodeficiency.
• Participant has a history of photosensitivity or photoallergy.
• Participant has a history of skin cancer or malignant melanoma.
• Presence of significant scars, tattoos, surgical incisions, or pigmented lesions (e.g., prominent birthmarks) in the test area that may affect assessment, and in the investigator's judgment, would impede normal imaging or scoring.
• Has used high-potency active products containing high concentrations of retinoic acid/retinol, alpha hydroxy acids, salicylic acid, etc., on the test area frequently (≥3 times per week) for an extended period (≥4 weeks) within the past 3 months, which, in the investigator's judgment, may significantly affect skin texture or barrier status.
• History of moderate to severe sun exposure (e.g., prolonged outdoor work, travel to seaside/high altitude) within the past 4 weeks, resulting in significant tanning or sunburn in the test area that, in the investigator's judgment, may interfere with study-related readings.
• Participation in other clinical or consumer testing projects involving the skin condition of the test area within the past 4 weeks.
• Presence of significant mental or cognitive impairment affecting compliance, and the investigator considers the participant unable to understand the study procedures or complete the tests as required.

Approximately 20 healthy Chinese female volunteers, aged 18-60 years with Fitzpatrick skin phototypes III, IV, or V. This population will serve as participants in a self-controlled, observational study to model laser-induced skin injury. Each participant will receive both ablative (CO2) and non-ablative (M22) fractional laser exposures with varying parameters on their inner forearms to observe the dynamic physiological response and recovery process.