Niacinamide is generally a reasonable choice for seborrheic dermatitis and may be helpful in some formulas. A small open randomised study of a 4% nicotinamide cream for mild to moderate facial seb derm reported a larger improvement than the vehicle cream. That is encouraging direct evidence, but it does not prove that every niacinamide serum will treat a flare.

Concentration and the rest of the formula still matter. A simple, comfortable moisturiser containing Niacinamide may suit irritated skin, while a strong or complex serum can still sting an active flare. Treat it as a potentially useful supporting ingredient rather than a replacement for a proven treatment plan, and stop if redness or burning repeatedly increases.