The short version….
In most cases, for a (topical application) to be biologically important (i.e., absorbed into your skin), it needs to have a Vitamin C (Ascorbic Acid) concentration MORE than Eight per cent.
Studies …show a concentration more than 20 percent does not increase its biological importance and, conversely, may cause some irritation.
Ravetti S et al, Ascorbic Acid in Skin Health. Cosmetics 2019, 6, 58; doi: 10.3390/cosmetics6040058
The long version: let’s talk about the science…
A long time ago in a galaxy we are in, Dr Pinell* (yup that guy (again)), and his colleagues conducted this experiment. They applied a range of 5% to 30% Vitamin C (L-Ascorbic Acid) solutions to pig skin (common practice) and their main findings were:
- Even at 5 per cent, Ascorbic Acid accumulates in the skin (so even LOW amounts of Vitamin C are good news)
- Ascorbic Acid levels in tissues INCREASED with concentration but plateaued at 20 per cent.
- For concentrations greater than 20% levels of L-Ascorbic Acid started to drop.
- Similar levels of L-Ascorbic Acid absorption occurs for both 10 per cent and 30 per cent.
Main takeaway: L-Ascorbic Acid concentrations above 20% are a waste.
Is there dissension in the ranks?
Yes. Some dermatologists and beauty brands violently disagree. The maximum concentration of powdered Ascorbic Acid I found was 100 per cent. The argument is that with a HIGHER concentration, simply more L-Ascorbic Acid is available to the skin.
What do I think?
Anything above 8% L-Ascorbic Acid is beneficial. Stick to an identifiable 15% – 20% L-Ascorbic Acid serum. Twenty plus L-Ascorbic Acid serums are a waste..
Are 20%+ Vitamin C serums common?
Unsurprisingly, 20%+ L-Ascorbic Acid products are uncommon, reflecting the fact that the rebellion is still in its infancy. If I were to a hazard a guess, scientists haven’t been able to refute the available clinical data that L-Ascorbic Acid uptake by the skin drastically starts to drop above 20%
That’s good news for us.
Products I would not buy because of the high Vitamin C content
Are there any other Vitamin C serums you would not buy?
Yes. So many. But I really want to highlight this group of absolutely hideously expensive serums.
No one needs to buy such expensive products and I don’t care if you are a billionaire.
Closing
Thankfully, there are few products in the category of high percentage Vitamin C serums and I would be weary of buying such products, even if they are cheap. See also, The Gold Standard Vitamin C serums, Should I be using a topical Vitamin C serum?
That’s it from me. Drop me a line at email@happyskindays.com if you have any queries or comments.
* Dr Pinnell
Dr Pinnell is the co-inventor of the Duke Anti-oxidant patent and more information is available at this blog.
Source
Topical L-ascorbic acid: percutaneous absorption studies. Pinnell SR1, Yang H, Omar M, Monteiro-Riviere N, DeBuys HV, Walker LC, Wang Y, Levine M.