Can I use Niacinamide 10% + Zinc 1% Serum with vitamin C products?. How often should I apply Niacinamide 10% + Zinc 1% Serum?. Is Niacinamide 10% + Zinc 1% Serum suitable for blemish-prone skin?. BOOSTS BRIGHTNESS & SMOOTHNESS: Niacinamide 10% + Zinc 1% visibly improves skin radiance and smooths texture in one week.