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Achieving an Even Skin Tone

By: Katerina Steventon, PhD
Posted: April 27, 2012, from the May 2012 issue of GCI Magazine.

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Interestingly, only a few actives that reduce pigmentation have been clinically tested. The application of 2% N-acetylglucosamine, for example, was shown to reduce the appearance of facial hyperpigmentation in an eight-week, double-blind, placebo-controlled, split-face clinical study.4 When N-acetylglucosamine was combined with 4% niacinamide, the efficacy was even greater.5 Niacinamide also demonstrated a significant decrease in pigmentation by inhibiting melanosome transfer during a four-week study.6

Traditionally, plants such as grapes and parsley were used for their active ingredients to reduce skin pigmentation. Other historical sources—including vitamin A, vitamin C derivatives, resveratrol, kojic acid and glycolic acid—have transferred from the pharmaceutical industry. The efficacy of these actives differs depending on their concentrations—typically ranging from 0.5–5.0% but also approximately 20% for the alpha hydroxyl acids—as well as source, stability and combination in the formulation types used.

Hydroquinone was the best established topical active for inhibiting melanin production despite its side effects of skin irritation. However, in September 2006 the U.S. Food and Drug Administration (FDA) recommended that products containing hydroquinone be sold only with a prescription due to its being a possible health risk as a carcinogen.7 Dermatologists still endorse the use of hydroquinone in concentrations of 4% and more, and over-the-counter skin care products, in some markets, contain it at levels of 0.5%–2%. 

Recent Ingredient Launches

With the increasing consumer demand for natural ingredients, two skin-lightening actives launched in 2010 are of particular interest. Liposome-encapsulated citrus flavonoids (including narirutin, naringin, hesperidin and neohesperidin) from grapefruit and bitter orange extracts have shown efficacy in reducing pigmentation, increasing luminosity and brightening skin tone by inhibiting tyrosinase. In a small eight-week study with a twice-daily application of 1% citrus extract complex, a 9.2% lightening of pigmentation and 5.0% brightening of skin tone in Caucasian facial skin was observed.8

In another study, a 6% complex of vitamin C, zinc pyrrolidone carboxylic acid (PCA) and oleuropein was applied twice daily on 20 volunteers directly on pigmentation spots. Results showed a reduction of the pigmented area by 21.2% after 12 weeks of use and the prevention of de novo formation of both melanin and lipofuscin.9

Conclusion