Q & A Vitamin C
From Dr Hannah Sivak
Question: What is the best way to ensure that your vitamin C serum is fresh and has not oxidized?
Answer: . My suggestion is that you make your own C serum or, even better, use our version. Why? We give you the double benefit of starting with L-ascorbic acid crystals (zero oxidation) and perfect formulation of the base serum, delaying by months any unwanted changes in the serum composition. In our serum, even if eventually you observe some changes in colour, these are unlikely to be related to oxidation of ascorbic acid.
Question: How long should we wait before putting on serum or cream after using the Vit C serum?
Answer: Left to itself, the skin may take a few hours to go back near its original pH, i.e. if you don't apply anything after the Vitamin C serum. But if you apply a different serum or a cream, the change back to near neutral pH will happen much sooner. I would not worry at all about the pH effect unless you wish to use serums containing delicate proteins, like EGF or thioredoxin.
Question:"How often should it be used if one's regime already incorporates other serums and creams" and "The best regime for anti aging that incorporates it without compromising other ingredients. Vitamin C Serum For Dummies, if you will."
Answer: It depends on your objectives, of course. But for older skin, I think (the acidic) ascorbic C serum could be used a couple of times a week, alternating with (the pH neutral) Collagen serum, which includes important active proteins like epidermal growth factor. And don’t forget Vitamin A, a retinoid, because it works in a completely different way and it is very useful in the treatment of wrinkles.