This was one of the first vitamin c serums I have tried. And the results were great (and fast), it significantly reduced the sun damage I have and it evened out my skin tone. In the beginning I used it every day, but it turned out to be too much for my skin so I reduced to 3 to 4 times per week. My only gripe with this product is that is oxidizes quickly so since I didn't use it on daily basis I had to throw it away after 2 months. It's a shame really since if was a more stable formulation it would be a great product otherwise.