Peptides in Aesthetic Dermatology: Classification, Fibroblast-Centered Mechanisms, Delivery Technologies, and...

Peptides used in aesthetic dermatology differ in molecular identity, biological target, formulation, and route of administration. This critical narrative review classifies these agents and examines their direct or indirect relationships with dermal fibroblasts, integrating mechanistic, delivery, and clinical evidence. Matrikine-like and copper-binding peptides influence matrix-related responses in experimental systems, whereas neuromodulatory and pigment-modulating peptides primarily act through other cellular targets. Oral collagen hydrolysates provide amino acids and circulating hydroxyproline-containing peptides with fibroblast activity demonstrated mainly in preclinical models. Lipidation, encapsulation, and microneedles can modify exposure, but delivery-system effects complicate attribution to the peptide. Controlled human studies report improvements in selected skin endpoints, including wrinkles, hydration, elasticity, dermal density, and pigmentation; however, many trials are limited by small samples, short follow-up, industry sponsorship, or multi-ingredient formulations. Current evidence supports product-specific interpretation rather than interchangeability across peptide classes or administration routes. It does not establish universal purity thresholds, commercial shelf lives, or safety of degraded formulations. Future studies should connect characterized composition and verified exposure with cell-specific mechanisms, objective clinical outcomes, and route-appropriate safety assessment.