There is a discussion in the cosmetic science forum asking about the stabilization of Vitamin C in a formulation. It is an interesting enough conversation and I encourage you to go read it. One of the points that came up was that Vitamin C doesn’t do much in the formula even if you could stabilize it. That prompted one of the people in the discussion to link a number of studies which demonstrated Vitamin C stabilized with Feurric acid could indeed provide UV protection.
Demonstrating an effect
The studies were also rather interesting and maybe they do show that Vitamin C can provide UV protection. However, one of the primary problems with the studies is a problem with many studies of cosmetic raw materials. They didn’t use the right controls. When testing whether Vitamin C could provide UV protection they had an untreated site as a negative control and they had an unexposed site as a positive control. From this they showed that Vitamin C provide some UV protection.
Unfortunately, this doesn’t help much for a formulator. We don’t simply want to know if there is some effect. We really want to know how does the effect compare to the best technology available. In this case, they should have done a control that featured a conventional UV protectant like TiO2 or Zinc Oxide. Why didn’t they do this?
I suspect if they did, they would have found that the Vitamin C does not provide as much protection as the standard technologies. And that makes sense. If they did provide that much protection they would be included in the monograph for sunscreens.
What’s a formulator to do?
But what if you want to create a Vitamin C based sunscreen? Simple, just create a standard sunscreen and add a drop of Vitamin C. You get all the marketing power of having Vitamin C in your formula but you get the performance of the best technology. It’s a win all the way around.
So I have to wonder, why would anyone not do it this way?