common reactions from high percentage niacinamide

1. Do the patch test - on the jawline or ear) 2. start using once a week first 3. then slowly upgrade to twice a week 4. well i don't usually use niacinamide serum everyday, so if you have sensitive skin it's better to use other hydrating or calming serum together 5. stop if you see any sign of irritation.

You can use combine niacinamide with other active ingredients too, but make sure your routine doesn't include more than 3 actives at one time.