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 ineffective 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.
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.
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.
Benefits of Vitamin C in Topical Skin Care Products:
When it comes to applying this vitamin topically at levels ranging from 0.3-10%, the benefits are:
- Potent antioxidant, particularly in regard to protecting skin cells from UV-induced damage
- Delays tumor formation after skin is exposed to extensive UV damage
- Has a low risk of skin sensitization at concentrations up to 10% in the form of ascorbic acid
- Reduces transepidermal water loss (TEWL), thus strengthening skin's barrier response
- Promotes collagen production and has the potential to thicken the dermis
- Reduces inflammation
- Ascorbic acid at levels of 5% and above has a positive effect on
hyperpigmentation (though the results are not as impressive as
hydroquinone, suggesting a combination of the two would be optimal)
- Improves the appearance of sun-damaged skin by strengthening skin's repair mechanisms
- Enhances the effectiveness of dermatologist-performed procedures such as peels and microdermabrasion
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