Niacinamide

Niacinamide is the amide form of vitamin B3, and one of the most studied ingredients in skincare. Its appeal is breadth: it has documented effects through several unrelated pathways rather than one.

Barrier lipids

Niacinamide is a precursor to nicotinamide adenine dinucleotide, a coenzyme involved in cellular energy metabolism. Research associates topical niacinamide with increased synthesis of ceramides and other barrier lipids, which is the basis of its reputation for supporting the barrier rather than merely sealing it.

Pigmentation

Niacinamide does not inhibit tyrosinase, the enzyme that produces melanin. Instead it appears to interfere with the transfer of melanin from melanocytes to surrounding keratinocytes. Pigment is still made, but less of it reaches the visible surface.

That is a different mechanism from most brightening ingredients, which is why niacinamide is frequently combined with them rather than substituted for them.

Sebum and inflammation

Studies have reported reduced sebum production at higher concentrations, and anti-inflammatory activity relevant to the appearance of redness.

On the vitamin C myth

Niacinamide and vitamin C are often said to cancel each other out. This originates in older research where the two were combined under heat, forming a complex. In modern formulations at skin-relevant temperatures, this is not considered a practical concern and the two are frequently formulated together deliberately.

Concentration

More is not linearly better. Most research supporting niacinamide's effects used concentrations between two and five percent. Higher percentages are marketed heavily and are more likely to cause flushing or irritation without adding benefit.