Is B12 useful for skin aging?

The evidence for vitamin B12 improving skin aging is weak and largely indirect. B12 is crucial for DNA repair, cell turnover, and melanin synthesis; deficiency can cause skin issues like hyperpigmentation, pallor, or premature wrinkling. Correcting a deficiency may restore skin health, but for individuals with adequate B12 levels, no high-quality human trials show that extra B12 reduces wrinkles or slows aging. Topical B12 has been studied for conditions like eczema and rosacea, not specifically for photoaging or chronological aging. The mechanistic rationale (involvement in collagen synthesis and oxidative stress) exists, but clinical proof is lacking. Most claims come from supplement marketing, not rigorous science. Evidence level: unclear/mechanistic. Safety: B12 is safe at standard doses, but megadoses are unnecessary. A better approach for skin aging includes sun protection, retinoids, and a balanced diet rather than relying on B12 alone.