Anhydrous vitamin C combo. Making the best of your vitamin C skin care.
Vitamin C (L-ascorbic acid) is one of the relatively few topical agents whose effectiveness against wrinkles and fine lines is backed by a fair amount of reliable scientific evidence. Unfortunately, the practical use of vitamin C in skin care presents some difficulties for a number of reasons. First, vitamin C is relatively unstable. When exposed to air, vitamin C solution undergoes oxidation and becomes not only ineffective but also potentially harmful (oxidized vitamin C may increase the formation of free radicals). Second, vitamin C products (especially the effective ones) tend to be irritating for many people. Topical vitamin C formulations need to be at least 10% strong to boost collagen synthesis and thereby improve wrinkles. At this concentration, vitamin C preparations are highly acidic (pH around 2.5), which may be irritating, especially for sensitive skin. Neutralizing the acidity does not solve the problem because buffered vitamin C becomes ionized, which markedly reduces skin penetration. At present, there are two practicable approaches to solving the above problems. They may be combined to maximize the chances of squeezing all possible skin benefits out of vitamin C.
Anhydrous vitamin C
One approach to improving vitamin C stability and reducing the potential for skin irritation is to use anhydrous vehicle, i.e. a topical base cream containing no water. Since water acts as a catalyst of vitamin C oxidation, anhydrous environment reduces the rate of vitamin C degradation. Anhydrous vitamin C is more stable not only during storage but also on the skin after the application. This is an important advantage, even compared to some stabilized water-based vitamin C formulas, which may store well but still oxidize quickly on the skin surface. Furthermore, anhydrous vitamin C tends to be less irritating than regular ascorbic acid products because the irritation is caused mainly by hydrogen ions generated by acid dissociating in water.
Vitamin C derivatives
Another solution is to use of vitamin C derivatives, which may provide skin benefits similar to the unmodified vitamin C (L-ascorbic acid) but tend to be more stable and less irritating. Unfortunately, vitamin C derivatives have limitations of their own. While a number of vitamin C derivatives appear promising as collagen boosters, more studies are needed to definitively determine which ones are as effective as vitamin C itself. Also, due to variation in individual skin biochemistry some people who respond to vitamin C do not respond to its derivatives and vice versa.
Anhydrous vitamin C combo, possibly the best of both worlds
There is some evidence that combining water soluble and oil-soluble forms of vitamin C may provide synergistic skin benefits through broader antioxidant protection and better penetration. However, combining high concentrations of oil and water-soluble active ingredients is often technically difficult using typical skin care vehicles. Fortunately, in the case of vitamin C, some anhydrous vehicles allow to combine high potency vitamin C with its oil-soluble derivatives while providing the extra stability of water-free base. For example, one can combine L-ascorbic acid (water soluble) and tetrahexyldecyl ascorbate (oil-soluble) in an anhydrous vehicle. A study of such a formula, conduced by Drs Fitzpatrick and Rostan, was published in Dermatological Surgery (a peer-reviewed journal) in 2002. The researchers used a combination of L-ascorbic acid and tetrahexyldecyl ascorbate in anhydrous polysilicone gel base applied to one-half of the face vs. inactive polysilicone gel base applied to the opposite side. The researchers concluded that the formulation produced "clinically visible and statistically significant improvement in wrinkling when used topically for 12 weeks" and that "the improvement correlated with biopsy evidence of new collagen formation."
While many biocompatible organic vehicles may be used as an anhydrous base (e.g. glycerin), the best results seem be obtained with siloxanes and polysilicones. These are related silicon-containing organic compounds often used as skin protectants. Siloxanes and polysilicones appear particularly effective in forming an anhydrous film that protects the skin surface from irritation, oxidation, and other offenses.
Unfortunately, as of the time of this writing, no commercial product seems to be an anhydrous vitamin C combo. Non-anhydrous products with vitamin C derivatives are available. So are a few anhydrous L-ascorbic acid products, although they tend to be rather expensive. While waiting for an anhydrous vitamin C combo to become commercially available, you can try to use both of these types of products. If you do, apply them at least a few hours apart. Applying a regular product (i.e. a product containing water) together with an anhydrous one reduces the benefits of the latter.
Alternatively, you can take a DIY route. Skin-friendly anhydrous bases are readily available. With minimal effort and expense, you can make anhydrous vitamin C and/or anhydrous vitamin C combo yourself.