Antioxidants Used in Skin Care Formulations

I. Bogdan Allemann, MD; L. Baumann, MD

Disclosures

Skin Therapy Letter. 2008;13(7):5-8. 

In This Article

Vitamin C

In humans vitamin C (ascorbic acid) can be obtained solely from food, such as citrus fruits. Sunlight and environmental pollution can deplete vitamin C present in the epidermis[25] and because vitamin C is a potent antioxidant, enhancing its levels in the skin seems reasonable. Vitamin C predominantly exists in its reduced form, ascorbic acid. Its oxidized form, dehydro-L-ascorbic acid can be found in trace quantities and can revert back to ascorbic acid. However, if the lactone ring irreversibly opens, diketogulonic acid is formed, which is no longer active. This happens when vitamin C preparations are oxidized, rendering them ineffective and useless.[26] Thus, vitamin C preparations should be kept in airtight, light-resistant containers to avoid exposure to UV rays or the air.

Topical vitamin C as a photoprotectant has been studied in vitro and in vivo, demonstrating its effects in preventing sun damage by reducing sunburn cells and decreasing erythema when exposed to both UVA and UVB irradiation.[27] The addition of topical vitamin C to either a UVA or UVB sunscreen was shown to improve sun protection when compared with sunscreen alone.[28] Furthermore, adding topical vitamin C to “after–sun’ products has been shown to scavenge UV-induced reactive oxygen species.[29]

Ascorbate is required for collagen synthesis[30] and the addition of ascorbic acid increases collagen production in human skin fibroblasts.[31] At the same time it may reduce production of elastin by an unknown mechanism.[32] Two studies in humans have shown an improvement in the appearance of wrinkles upon topical application of vitamin C.[33,34] However, more clinical trials are necessary to unravel all the effects of vitamin C on skin and aging. Thus, vitamin C preparations are useful in preventing or lessening the detrimental effects of UV radiation. Some patients experience minimal discomfort (stinging and mild irritation) from topical application.

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