L-Carnitine in Dermatology: A Systematic Review of Therapeutic Potential and Biomarker Applications.

L-Carnitine, an amino acid derivative critical for fatty acid metabolism, exhibits anti-inflammatory, antioxidant, and cytoprotective properties, with emerging applications in dermatology. This review explores its therapeutic potential, both topically and systemically, and its role as a biomarker in various skin disorders. A systematic search of Medline, EMBASE, and PubMed (1946-January 2025) was conducted, focusing on L-carnitine and dermatologic conditions, excluding acetyltransferases, acyltransferases, breast, and genetic metabolic diseases. From 420 articles, 59 were included after screening in Covidence. Data on study design, sample size, carnitine type, and outcomes were extracted and validated by two authors. Topically, L-carnitine (1%-5%) reduces acne lesions, sebum production, post-inflammatory hyperpigmentation, and cellulite, particularly when combined with agents like licochalcone-A or salicylic acid. Systemic L-carnitine mitigates inflammation, oxidative stress, and treatment-related side effects (eg, from corticosteroids, isotretinoin, vismodegib) while improving skin elasticity, microcirculation, wound healing, and fibrosis in conditions like Raynaud's disease, venous leg ulcers, and sclerotic disorders. As a biomarker, altered carnitine levels and metabolites reflect disease mechanisms in genodermatoses (eg, restrictive dermopathy, recessive dystrophic epidermolysis bullosa), inflammatory dermatoses, and melanoma, aiding diagnosis and monitoring. L-Carnitine shows promise as a therapeutic and diagnostic tool in dermatology, with benefits in acne, sebum control, post-inflammatory hyperpigmentation, cellulite, inflammation, and tissue repair. Its biomarker potential enhances disease insights and personalized care. Further dermatology-specific trials are needed to optimize dosing, formulations, and long-term safety, particularly regarding trimethylamine-N-oxide-related cardiovascular risks.