After 4 days of using this, I have seen a big difference in pore size and overall skin texture. Niacinamide is amazing for reducing the amount of free radicals in your cells which damage your skin cells. Niacinamide boosts barrier function by increasing ceramide production, to aid better water-retention and overall skin structure. Ceramides make up 50 per cent of the uppermost layer of the skin and are fatty acids that maintain the skin barrier and retain moisture, keeping the skin hydrated. For having slightly sensitive skin, I have found the 10% potent enough, i’ve not experienced any irritation. Typically you should not experience purging with Niacinamide, if you do you need to use a lower %. Zinc is amazing for balancing the pH of your skin which may be altered by some strong masks/ serums or air pollution. 10/10 product!!