I'm in my second bottle of this Vitamin C serum, and since the beginning, I noticed how my oily skin adapted to this serum, without oily skin in the middle of the day or new pimples, but the most amazing thing was a little dark spot I had below my left eye zone, that I noticed today to be much less visible, almost gone. I'm going to continue using it and see if it disappears totally.

Mich interessiert der Geruch, den viele bemängeln, überhaupt nicht, der verfliegt innerhalb weniger Sekunden. Die Formulierung dieses Serums zu so einem Preis?!? Wie geht das? Schön mehrfach nachgekauft

Ascorbic acid, the original form of Vitamin C, is a pain to work with for beauty product. It's unstable, smelly, and only works in lower pH unless it's specially processed. But it works and good for skin tone. Some products are very expensive, and when it turns yellow it's really a waste. I am a biologist and I usually make my own Vit C serum with Vit C powder + baking soda, but I buy this product because: 1. it has many other goodies; glutathione, feuric acid, Vit E... 2. the company is transparent about the stability issue and limit the shelf life to three months, assumingly the product is fresher than those stay on shelf for half year. 3. it's really quite cheap, so even you don't finish it in three months, you don't feel much pain.
It has a odour, like most of ascorbic acid serum has; the odour of this product is stronger possibly due to glutathione. Glutathione is even less stable than Vit C so I still keep this serum in the fridge. The only concern from me is that I checked the pH of this product today, it seems to be around 4. Vit C needs lower pH to be absorbed, unless it has penetration enhancer. There are some in the ingradients list but I am not sure how effective they are.