Poly-L-Lactic Acid in Aesthetic Dermatology: Injection Techniques, Clinical Protocols, Skin Quality Outcomes, and Risk Management

Poly-L-lactic acid is a synthetic, biodegradable collagen biostimulator that has evolved over more than two decades from a corrective agent for human immunodeficiency virus-associated facial lipoatrophy into a widely used tool in regenerative aesthetic dermatology.Unlike hyaluronic acid fillers, which provide immediate volume by occupying space, it acts indirectly: its microparticles elicit a controlled subclinical foreign-body response that drives macrophage polarization, transforming growth factor-beta 1/Smadmediated fibroblast activation, and progressive type I neocollagenesis.In this narrative review, PubMed/MEDLINE, Embase, and the Cochrane Library were searched through August 2026 for Englishlanguage, peer-reviewed studies, which were appraised narratively to summarize the evidence on injection techniques and reconstitution, clinical protocols and patient selection, clinical efficacy and skin quality outcomes, and the prevention and management of complications.Consensus statements and comparative studies associate higher reconstitution volumes, thorough suspension, subdermal placement, non-bolus delivery, and structured post-treatment care with fewer papules and nodules, although much of this guidance rests on expert opinion and observational data rather than head-to-head trials.A small number of randomized controlled trials report improvements in cheek wrinkle severity, skin elasticity, hydration, and dermal thickness compared with no treatment or saline, and indications are extending to the neck, décolletage, body, and patients with facial volume loss during glucagon-like peptide-1 receptor agonist therapy.However, the available trials are few, heterogeneous in protocols and outcome measures, and frequently at some or high risk of bias.Non-inflammatory nodules and inflammatory granulomas differ in mechanism and are managed along distinct pathways.Standardized protocols, a core outcome set for skin quality, and adequately powered comparative trials are needed before firm conclusions about the relative effectiveness of poly-L-lactic acid can be drawn.