Niacinamide

Niacinamide is 烟酰胺 (yān xiān àn) in Chinese — 菸鹼醯胺 in Traditional Chinese as used in Taiwan — also sold as 维生素B3 (vitamin B3). It's a multitasking active that regulates oil, reinforces the skin barrier, and calms inflammation.

No. 4–5% is already clinically effective, and 10% is the safety ceiling. Above that, redness and stinging become likely. Sensitive skin should start at 2–3% and work up gradually — it's the safer route.

Yes, but separate them. High-dose niacinamide is mildly alkaline while vitamin C needs an acidic environment to absorb, so mixing makes them interfere. Use niacinamide in the morning and vitamin C at night, or leave 20+ minutes between them.

Likely too high a concentration or low tolerance. Stop for 1–2 weeks, then restart with a lower-strength product from 2%. If the redness persists, your barrier is probably compromised — repair it first, then reintroduce.

Oil control typically shows in 4–6 weeks; barrier repair takes 8–12. Use it morning and night with a lightweight moisturizer for best results. Don't expect complete oil control within a week.

There are no adequate pregnancy safety studies. Low concentrations are theoretically low-risk, but to be safe, check with a dermatologist or OB before using it while pregnant.