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I never thought that I would even mildly like a vitamin C serum in a clear jar. But Kiehl’s Clearly Corrective Dark Spot Solution ($49.99, Amazon.com) gets a semi-nod: it’s likely to work, though not as well as concentrated L-ascorbic acid serums like Skinceuticals CE Ferulic.
It contains a stable form of vitamin C, 3-O Ethyl Ascorbic Acid, that fares better in the presence of light and air, plus vitamin E and a solid delivery system. Overall, I like it because it’s likely to work, albeit slowly. Also note other products on the market are better for sunspots, including concentrated L-ascorbic acid serums and 4% hydroquinone. For more, read on.
3-O-Ethyl Ascorbic Acid
In a similar way, 3-O-Ethyl ascorbic acid is a derivative consisting of vitamin C and an ethyl group that is proving to be stronger and more stable than ascorbic acid, at least in early studies. In a clinical skin lightening test by Spincontrol France, a solution containing just 2% 3-O-ethyl ascorbic acid was found to improve skin whitening and radiance after just 28 days of twice-daily application (Cosmetics and Toiletries). Keeping in mind that similar results are produced in separate studies with 15% L-ascorbic acid— 7 times as much! — this means that 3-O-Ethyl ascorbic acid certainly holds promise.
As for stability, the only difference between 3-O-Ethyl ascorbic acid and ascorbic acid structurally is that the former has an ethyl group bound to the third carbon position — but it makes a big difference. What this means in plain English is that 3-O-Ethyl ascorbic acid is more stable in the presence of light, heat, and air than ascorbic acid when used in cosmetic products. Samples of 2% 3-O-Ethyl ascorbic acid have been retained for 1 month in a 45°C (113°F) oven, and there was no change in color or purity (Cosmetics and Toiletries).
So I do believe that esters of some of our favorite active ingredients at FutureDerm are the future of skin care — retinyl retinoate instead of retinol, for example, or 3-O-ethyl ascorbic acid instead of L-ascorbic acid. Truth be told, I do say the future because I would like to see studies directly comparing the efficacy of each set of these ingredients head-to-head before I personally go back and change my entire skin care regimen to ester-based derivatives of active ingredients. But, I do see it as a distinct possibility in the near future.
Solid Delivery System
If I spent my early twenties learning about boys (and finally finding the right one!), I spent my late twenties learning about skin care delivery systems.
I kid you not – just as the opposite sex can put you through the ringer, so can delivery systems. Contrary to popular belief, neither propylene glycol nor alcohol are harmful or detrimental to the skin in beauty products. Instead, they both help deliver key ingredients deep within the skin. Propylene glycol is incredibly effective in getting ingredients into the skin – so much so that it’s the same ingredient used in nicotine patches.
On the other hand, alcohol thins a solution, allowing the thick layers of a formulation to be compressed. If many skin care formulations didn’t contain alcohol, they would rest on top of the skin, never delivering key ingredients. That’s not to say you should use pure alcohol on your skin regularly – this would dry it out. But in the context of other ingredients, alcohol dries them out – not your skin. This is a mistake I made early on in my days at FutureDerm, and I’m sorry about the misunderstanding.
Why is it in a clear bottle?
My other problem with Kiehl’s Clearly Corrective Dark Spot Solution is that it is in a clear bottle. When it comes to light and air, vitamin C is one of the most reactive skin care ingredients out there. Sure, 3-O-ethyl ascorbic acid is certainly more stable than L-ascorbic acid, but I have studied many ascorbic acid derivatives, and none are completely unreactive to light and air.
There’s no need to provoke vitamin C in a clear bottle. A better option: a dark amber bottle (for Kiehl’s) or placing Kiehl’s Clearly Corrective Dark Spot Solution back in the box quickly following each use.
I know a lot of women who love Kiehl’s. It’s probably a combination of the fact that Kiehl’s has some high-quality products, and that their marketing budget went way up after they were acquired by L’Oreal a few years ago. But I digress.
I like Kiehl’s too, so I will say this: If you want the best vitamin C or sunspot treatment on the market, don’t buy Kiehl’s Clearly Corrective Dark Spot Solution. But if you swear by Kiehl’s and only want to use their products, then I will tell you that you will get results from Kiehl’s Clearly Corrective Dark Spot Solution, albeit slowly.
Product Rating: 7.5/10
- High or optimized concentration of independently proven ingredients: 2/3
- Unique formulation or new technology: 3/3
- Value: 2.5/3
- Sunscreen-boosting antioxidants: 1/1