Niacinamide.

Niacinamide (Vitamin B3) inhibits melanin transfer to skin cells, regulates sebum secretion, strengthens the ceramide barrier, and reduces pore appearance. At 10%, it does all four simultaneously -- the single most efficient active for the combination-oily, PIH-prone South Indian skin profile.

Pairs with most actives. Avoid combining high-concentration Vitamin C in the same step -- apply separately or use a stabilised Vitamin C form. Fragrance-free formulations only for South Indian skin to prevent irritation-driven PIH.