Vitamin C, or ascorbic acid, has a long history of topical use and is one of the most researched active ingredients used in skin care. Vitamin C is the major water-soluble antioxidant found in the body and a cofactor in at least eight important enzymatic reactions. As an antioxidant, it destroys free radicals and plays a major role in hydroxylation reactions essential for the formation of collagen.
Humans are one of the few mammals that can’t produce vitamin C, because they lack the enzyme L-gluconolactone oxidase, which converts glucose to ascorbic acid. Vitamin C is normally found at high levels in the dermis and epidermis. A study of vitamin C in young, aged and photo-damaged human skin demonstrated that vitamin C levels were 31 percent lower in the epidermis of photo-damaged skin and 39 percent lower in aged skin. In the dermis, vitamin C levels were 37 percent lower in photo-damaged skin and 30 percent lower in aged skin. Environmental pollutants, such as ozone, can also decrease vitamin C levels in the skin and lead to free-radical damage. Additionally, smoking can lead to increased wrinkling and decreased collagen synthesis, which corresponds to a decline in plasma vitamin C levels.
Ascorbic acid was the second generation of skin-care actives launched in the 1980s following the success of alpha-hydroxyl-acid-based products (AHA). However, due to vitamin C’s poor water stability, cosmetic formulations were limited to anhydrous solutions and emulsions. Under aerobic conditions it can reversibly oxidize to dehydroascorbic acid (DHA), which can be irreversibly degraded to oxalic acid.
The use of vitamin C (3 to10 percent) in topical applications for at least 12 weeks has been shown to decrease wrinkling, reduce protein fiber damage, decrease apparent roughness of skin and increase production of collagen. Topical vitamin C has also been shown to reverse some of the age-related changes in the epidermis. However, topical vitamin C doesn’t appear to work for all individuals. One study demonstrated that individuals with high dietary intakes of vitamin C showed no or little topical effect.
Other studies have shown that a formulation containing 10 percent ascorbic acid (water-soluble) and 7 percent tetrahexyldecyl ascorbate (lipid-soluble) in an anhydrous polysilicone gel base clinically improved skin wrinkling when used topically for 12 weeks. A topically applied 5 percent vitamin C lotion was also shown to be highly effective at repairing aged skin, inducing significant collagen synthesis in all age groups with minimal side effects.
Claimed skin benefits for vitamin C and its derivatives:
- Acts as an antioxidant
- It has been shown to reduce the oxidation of squalene in sebum, which contributes to acne
- Reduces fine lines and wrinkles and may thicken the epidermis
- Reduces UV-induced redness and inflammation
- Lightens skin
- Improves acne
- Improves gingivitis
Recommended vitamin C derivatives:
- ET-VC (3-O-ethyl ascorbic acid by Corum): water-soluble derivative stable from pH 4.0 to 5.5. It contains the highest concentration of ascorbic acid of any vitamin C derivative (86.3 percent) and has probably the best skin penetration. It claims to be superior to sodium ascorbyl phosphate, magnesium ascorbyl phosphate and ascorbyl glucoside for skin lightening and requires no enzymatic conversion for skin activity. In a 28-day study on Asian skin, a 2 percent formulation was shown to significantly lighten skin. It is approved as a quasi-skin-lightening active in Japan at 1 percent.
- AA2G (ascorbyl glucoside from Hayashibara by DKSH): A water-soluble derivative stable from PH 5.0 to 8.0. When topically applied, it is hydrolyzed by endogenous α-glucosidase to the active ascorbic acid form. A 2 percent cream demonstrated a significant improvement in skin lightening after 90 days (4 L-value units) and a 39 percent improvement in wrinkle depth. It is approved as a quasi-skin-lightening active in Japan.
- BV-OSC (tetrahexyldecyl ascorbate by Nikkol Chemical and Barnet Products): An oil-soluble stable form, claimed to penetrate skin better than ascorbic acid, ascorbyl glucoside, and magnesium ascorbyl phosphate. It is approved as a quasi-skin-lightening active in Japan at 3 percent.
- Stay-C 50 (sodium ascorbyl phosphate by DSM Nutritional Products): A water-soluble, stable derivative at pH 5.0 to 7.0. A 5 percent lotion in a 12-week acne clinical was shown to be more effective than 5 percent benzoyl peroxide, a monographed active. The mechanism of action is believed to be antimicrobial and suppression of squalene oxidation. It is approved as a quasi-skin-lightening active in Japan.
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- Formulate at the recommended pH.
- Always use a chelating agent.
- Add to formulation below 40°C
- Because vitamin C derivatives are UV-sensitive, do not use clear packaging.
- Michaels AJ. Vitamin C and Skin Health. 2011 Sept. Corvallis, OR: Oregon State University; [accessed 2016 July 12]. http://lpi.oregonstate.edu/mic/micronutrients-health/skin-health/nutrient-index/vitamin-C
- Shindo Y, Witt E, Han D, Epstein W, Packer L. 1994. Enzymic and non-enzymic antioxidants in epidermis and dermis of human skin. J Invest Dermatol.102:122-124.
- Fitzpatrick RE, Rostan EF. 2002. Double-blind, half-face study comparing topical vitamin C and vehicle for rejuvenation of photodamage. Dermatol Surg. Mar; 28(3):231-6.
- Crisan D, Roman I, Crisan M, Scharffetter-Kochanek K, Badea R. 2015. The role of vitamin C in pushing back the boundaries of skin aging: an ultrasonographic approach. Clin Cosmet Investig Dermatol. Sep 2; 8:463-70.
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