Phototherapy for Acne Vulgaris: Strategies and Clinical Applications in Sebum Modulation, Inflammation Control, and Scar Management.

Background: Acne vulgaris is a chronic inflammatory skin disease, and photo-based therapies have been adopted as noninvasive alternatives to pharmacological treatment.Objective: To systematically evaluate the therapeutic strategies and biological mechanisms of photo-based therapies in the management of acne vulgaris, focusing on sebum modulation, inflammation control, and the treatment of acne sequelae to inform phenotype-oriented clinical decision-making.Methods: Following PRISMA 2020 guidelines, a systematic search was conducted in PubMed and Web of Science for studies published between 2005 and 2025. From an initial 2,218 records, 64 articles comprising 42 clinical trials and 22 experimental studies were selected for inclusion based on their focus on the efficacy, safety, and molecular mechanisms of light-emitting diodes (LED), intense pulsed light (IPL), laser systems, and photodynamic therapy (PDT).Results: Analysis revealed that photo-based modalities target acne through three primary pathways: 1. Sebum Modulation: Aminolevulinic acid (ALA)-PDT demonstrates superior, durable efficacy in moderate-to-severe acne by inducing sebocyte apoptosis and downregulating lipogenesis via the PI3K/Akt/mTOR and OLR1-Wnt/β-catenin pathways. 2. Inflammation Control: Blue and red light (LED) and IPL provide gradual anti-inflammatory effects suitable for mild-to-moderate acne by reducing C. acnes colonization and modulating cytokines such as TGF-β1, IL-10, and TNF-α. 3. Tissue Remodeling: For acne sequelae, fractional CO2 and picosecond lasers promote collagen remodeling to improve atrophic scars, while vascular-targeted lasers (PDL, Nd:YAG) and IPL effectively reduce post-inflammatory erythema (PAE) and hyperpigmentation (PIH).Conclusions: Photo-based therapies are phenotype-specific rather than interchangeable. Strategies targeting sebaceous activity and inflammation are central to treating active lesions, while tissue-remodeling interventions are most effective for managing sequelae. This review establishes a strategy-oriented framework that supports personalized, evidence-based treatment planning in routine clinical practice.