Consumer Perspective: Achieving an Even Skin Tone

By: Katerina Steventon, PhD, FaceWorkshops

Posted: February 2, 2012, from the February 2012 issue of Cosmetics & Toiletries.

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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, compared with a vehicle alone, 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 such as magnesium-l-ascorbyl-2-phosphate (MAP), N-undecylenoyl phenylalanine, resveratrol, arbutin, kojic acid, glycolic acid, azelaic acid and other compounds 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 ~20% for the alpha hydroxyl acids—as well as source, stability and combination in the formulation types used. The chemical structures of some of these skin-lightening actives, including hesperidin, oleuropein, niacinamide and vitamin C (ascorbic acid) are shown in Figures 1–4.

Hydroquinone was the best established topical active for inhibiting melanin production despite its side effects of skin irritation. However, in September 2006 the US 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 contain it at levels of 0.5%–2.0%.

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, 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^b 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

New anti-aging skin care products must focus on both textural and color features of the skin, as skin color has been shown to play an important role in the perception of youth and attractiveness. For the formulator, it is important to consider that short-term brightening skin care products like spot treatments, peels, exfoliators and masks require higher levels of active ingredients to achieve efficacy. Daily use moisturizers to even skin tone, however, must employ the correct levels of actives to lighten skin while not negatively impacting the skin barrier function. In the clinical tests described, typical levels ranged from just 0.5–6.0%.