The vitamin duo Korean estheticians always combine for even, luminous skin tone

Niacinamide and vitamin C: two mechanisms that work on different stages

Niacinamide (vitamin B3) inhibits the transfer of melanin from melanocytes to keratinocytes — it doesn't stop melanin from being produced, it stops it from reaching the skin surface cells. Vitamin C (ascorbic acid and derivatives) inhibits tyrosinase, the enzyme that produces melanin at the source. Together, they address pigmentation at both stages of the formation process: production and transfer. The combination is consistently rated more effective for uneven skin tone than either ingredient used alone because the two mechanisms reinforce rather than duplicate each other.

Why "no.5" became a shorthand for the niacinamide brightening serum category

In K-beauty product numbering systems (particularly prominent with Korean brands that number their products by concentration or function), a vitamin concentration system used by some brands created a shorthand among beauty editors: "no.5 serum" or similar number codes that signal the vitamin complex concentration or formula number. The number-coded formula approach gives consumers a clear reference point for comparing products within a range and tracking what concentration works for their skin. High-concentration vitamin serums named by formula number have become some of the most reviewed K-beauty products in the global market.

Layering niacinamide and vitamin C in the K-beauty routine without cancellation

The concern that niacinamide and vitamin C cancel each other out is outdated and has been refuted by modern formulation research. They can be used in the same routine — but for maximum efficacy, apply vitamin C first (as the thinner, lower-pH serum) and niacinamide second (at a slightly higher pH), waiting three to five minutes between applications. Alternatively, use vitamin C in the morning (before SPF, where it also provides antioxidant UV protection) and niacinamide in the evening for two distinct brightening windows.

Numbuzin No.5 + Vitamin Concentrated Serum 30ml — available on BuyBeautyKorea →