Vitamin C is one of the most widely used skin care ingredients. The variety of skin rejuvenation / anti-wrinkle products with vitamin C is staggering. Do these products work? Do their claims have any substance? The situation is a little complicated. On one hand, vitamin C does possess definite, scientifically validated merits for wrinkle reduction and skin rejuvenation. On the other hand, many vitamin C products do not work.
Potentially, vitamin C can benefit skin in two important ways. Firstly, vitamin C is essential for the synthesis of collagen, a key structural protein of the skin. Adding vitamin C to a culture of skin cells (fibroblasts) dramatically increases the synthesis of collagen. Secondly, vitamin C is an antioxidant and can help reduce skin damage caused by free radicals. So, when vitamin C is properly delivered into skin cells, there is a good chance to reduce wrinkles and improve skin texture.
There are, however, some complicating circumstances often disregarded by manufacturers. In particular, ascorbic acid, the principal natural form of vitamin C, is relatively unstable (unless it is in a dry form). In the presence of air or other oxidizing agents, it undergoes oxidation. The first step of ascorbic acid oxidation is conversion to dehydroascorbic acid (DHAA). This, in itself, might not be a problem since dehydroascorbic acid is also a natural form of vitamin C that can converted back to ascorbic acid in the body. Some even advocate using DHAA (or a mixture or ascorbic and DHAA) instead of pure ascorbic acid in skin rejuvenation formulas because DHAA is better at penetrating the skin. The merits of this approach require further research. At this point we can only say that the oxidation of a modest fraction of ascorbic acid in a skin care formula to DHAA is unlikely to make the formula ineffective.
Unfortunately, the story of ascorbic acid instability does not end with oxidation to DHAA. The problem is that DHAA is at least as unstable as ascorbic acid in water-based formulations, and so it is rapidly degraded into other breakdown products that are not forms of vitamin C. These breakdown products include organic acids that make the skin care product more acidic, so it is more likely to be irritating to the skin. Further degradation ("browning") imparts a yellow or brown color to the skin care product, which can stain clothing and bedding. In poorly prepared or poorly stored skin care products, vitamin C may already be degraded by the time you apply it to your skin. Since only highly concentrated formulations (10% or more) deliver enough ascorbic acid to the cells to be topically effective, degraded products might not be effective, and as stated above, may be more irritating to the skin and cause annoying stains on clothing.
A number of skin care companies offer highly concentrated stabilized vitamin C products, which (at least in theory) are supposed to be consistently effective. However, these products are usually quite expensive. Furthermore, even stabilized vitamin C products may be at least somewhat degraded by the time you use them. Interestingly, some manufacturers add coloring to their vitamin C products, in which case it becomes hard to spot advanced vitamin C degradation. Whatever the motives for adding color may be, we recommend avoiding vitamin C products that aren't colorless or white. When selecting a vitamin C product it is important to pick a trustworthy source and be careful about the expiration date and proper storage.
If you are willing to invest a bit of extra time, you can easily make a vitamin C gel or serum on your own. That way you ensure both freshness and potency - not to mention substantial cost savings. (For more information on making your own skin care, including vitamin C formulations, see our article Do-It-Yourself Anti-Aging Skin Care.)
Even when using an optimal formulation, not everyone will respond to vitamin C treatments. About 50% of people show noticeable benefits. The chances are improved when vitamin C is a part of a comprehensive regimen to rebuild collagen in your skin. (See our article on collagen.) Also, people who do not respond to conventional vitamin C products may respond to its derivatives, such as magnesium ascorbyl phosphate, ascorbyl palmitate and others. These vitamin C cousins not only boost collagen synthesis but also are more stable and less irritating. (See our article on vitamin C derivatives.)
Finally, keep in mind that taking large amounts of vitamin C (or its derivatives) orally is of little benefit for reducing wrinkles because you cannot obtain high enough concentration of vitamin C in the skin to increase collagen production.