Most Popular in:
Skin Lightening Challenges
By: Zoe Diana Draelos, MD
Posted: February 3, 2009, from the February 2009 issue of GCI Magazine.
page 4 of 5
Some studies indicate that kojic acid is equivalent to hydroquinone in pigment-lightening ability.10 The activity of kojic acid is attributed to its ability to prevent tyrosinase activity by binding to copper. The problem with kojic acid is again the ability to penetrate the skin and reach its copper target. It is possible that penetration enhancers might overcome some of this difficulty; however, damage to the skin barrier and product irritation are common side effects.
Aleosin is a botanical low-molecular-weight glycoprotein obtained from the aloe vera plant. It is a natural hydroxymethylchromone that functions by inhibiting tyrosinase.11, 12 In contrast to hydroquinone, it shows no cell cytotoxicity; however, it has a limited ability to penetrate the skin due to its hydrophilic nature. It is sometimes mixed with arbutin to enhance its skin lightening abilities.
Arbutin is obtained from the leaves of the Vaccinicum vitis-idaea (lingonberry) and other related plants such as bearberry, cranberry, mulberry or blueberry shrubs. It is a naturally occurring gluconopyranoside with a form of hydroquinone that causes decreased tyrosinase activity without affecting messenger RNA expression.13 It also inhibits melanosome maturation.
Arbutin is not toxic to melanocytes and is used in a variety of pigment lightening preparations in Japan at concentrations of 3%. Higher concentrations are more efficacious than lower concentrations, but a paradoxical pigment darkening may occur due to skin irritation. Synthetic versions of arbutin, such as deoxyarbutin, may offer enhanced efficacy.
The most effective skin lightening agents are ingredient combinations that use complementary mechanisms of action to lighten the skin. One of the most effective prescription combinations contains hydroquinone, tretinoin and a topical corticosteroid. The synergistic effect of the ingredients results in the superior results. Hydroquinone functions to inhibit tyrosinase, while tretinoin acts as a penetration enhancer, inducing stratum corneum sloughing to allow the hydroquinone to fully reach the melanocytes. In addition, tretinoin decreases pigment transfer.
Unfortunately, both hydroquinone and tretinoin are irritants, thus the addition of a topical corticosteroid increases the tolerability of the formulation while decreasing inflammation. Since inflammation is a driving force for skin pigmentation, the effect of the corticosteroid is also additive.