Is B12 useful for Haut?

Vitamin B12 (cobalamin) is relevant for skin health primarily in cases of deficiency. B12 deficiency can cause hyperpigmentation, vitiligo-like changes, and glossitis. The underlying mechanisms involve B12's role in DNA synthesis, cell division, and melanin regulation. However, in healthy individuals without deficiency, there is no robust evidence that additional B12 supplementation improves skin quality. Some studies even link high B12 serum levels to acne, possibly via alterations in skin microbiota. The evidence for a benefit of B12 for skin in non-deficient individuals is weak and largely mechanistic. A blood test for holotranscobalamin can detect functional deficiency. Supplementation is justified only when deficiency is confirmed; indiscriminate use for skin health is not evidence-based. Caution is warranted with high doses, as they may trigger acne in susceptible individuals.