When to apply #Vitamin C cream
Dear danatheFA: You have discovered Retin A and vitamin C, which are very effective in remodeling the skin, correcting and preventing aging and sun damage, and improving conditions such as acne, rosacea, and discoloration. You may use a vitamin C serum or cream at any time of the day that you wish, but there are a few caveats. #VitaminC is highly unstable and will only penetrate the skin at a very low pH. This means you must apply it to clean skin and allow it to penetrate for at least one hour before putting anything on top of it. You should also be sure you are using a pure L-ascorbic acid type of vitamin C that is at least 10% in concentration and that has a pH of 3.2 or lower. This means that a vitamin C product that has sunscreens or other ingredients in it that might lower the concentration or increase the pH will not work. For a product that meets these criteria, please see the link below.