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Product Review: Kiehl’s Highly Efficient Skin-Tone Corrector

Posted Feb 18 2009 11:47am 1 Comment


Without the requirement of FDA approval for many products, cosmetics companies can introduce new formulations and ingredients to the skin care market at an alarming rate.  In fact, MIT biologist and genetics researcher Dr. Leonard Guarante, Ph.D., states in the March 2009 Elle, “Beauty companies are able to get products on the market early because they’re not regulated by the FDA…In a way, they’re the vanguard.”  That’s clearly evident with  Kiehl’s Highly Efficient Skin-Tone Corrector  ($50.00,  Kiehl’ ), which features 4% glycolic acid (many dermatologists offer 10-40% during in-office treatments), together with new glycolic acid stabilizer and antioxidant, emblica (2%), and pH buffer, 5% hepes.  

The benefits of  glycolic acid  are well-established.  Glycolic acid, an AHA, is known for its ability to increase cell turnover and to refresh the overall look of the skin.  According to  Dr. David E. Bank, author of  Beautiful Skin,  alpha hydroxy acids cause increase exfoliation of the outer layer of skin, unplog pores, hydrate the skin,  reverse sun damage in the epidermis, and stimulate collagen and elastin production in the dermis.  And while the epidermis is thinned after use of AHAs, the overall thickness of the skin has been found to be increased after use of glycolic acid, as  treatment has been shown to increase expression of Type 1 Collagen mRNA and hyaluronic acid content  in the dermis of the skin.   So, obviously, 4% glycolic acid in  Kiehl’s Highly Efficient Skin-Tone Corrector  is a good choice.  (Just take care to use the product at night and in conjunction with daytime sunscreen use, as glycolic acid can make the skin photosensitive).  

Emblica, a natural ingredient derived from the Indian gooseberry, is relatively new to western skin care.  A  2002 study in Skin Pharmacology and Physiology  lauded the ingredient for its spectacular “long-lasting antioxidant properties.” Another  2005 study from the Asian Pacific Journal of Cancer Prevention  found that topical application of emblica extract on the skin of mice prevented cancer development, and attributed the finding to the antioxidant properties of emblica.  Most excitingly,  a 2008 study in the Journal of Ethnopharmacology  determined that emblica extract promotes procollagen production and inhibits matrix metalloproteinase-1 (which degrades collagen) in human fibroblasts in vitro; whether or not these results are replicable outside of the lab, time will tell, but it does look promising.  Kiehl’s, for one, is adding emblica not only for its antioxidant and collagen-building properties, but also for its ability to stabilize glycolic acid, according to the company’s October 2008 press release.  

I find the addition of 5% hepes in the product to be rather genius.  Hepes (Hydroxyethylpiperazine Ethane Sulfonic Acid) is an organic chemical buffer that is often used in cell cultures to maintain physiological pH.  What makes it so effective here is that glycolic acid has been found to have increasing efficacy with increased pH, according to  a 1996 study in Dermatologic Surgery.  Since glycolic acid has an approximate pH of 2.5-4.0 (depending on the concentration of the solution), by adding hepes, you are effectively increasing the pH of the solution (and hence the efficacy of the glycolic acid).  Pretty revolutionary!

The efficacy of the ingredients were confirmed in a 2008 (non-published) clinical study conducted by Kiehl’s.  In the product’s October 2008 press release, patients of  dermatologist Dr. Adam Geyer  reported “significantly diminished appearance of mottled pigmentation, UV sun spots, and uneven skin tone” after six weeks, and more dramatically so after sixteen weeks.  The efficacy was “comparable to 2% hydroquinone.”  (For the record, prescription strength is 4% hydroquinone).  Unfortunately, these results have not been replicated in a published study that is not affiliated with Kiehl’s.

Overall, I’m pretty excited by  Kiehl’s Highly Efficient Skin-Tone Corrector, and I personally think it makes a great nighttime hyperpigmentation treatment.  I look forward to learning more about emblica in the future, and I think the addition of hepes was genius.  I give this one a solid  8.5/10.  (High concentration of well-proven ingredients: 3/3.  New formulation: 3/3.  Value for the money: 2.5/3 - a bit pricey for a 4% AHA treatment, but still worth the buy.  Sunscreen: 0/1). 

Ingredients in Kiehl’s Highly Efficient Skin Tone Corrector

Aqua/Water, Glycerin, Hydroxyethylpiperazine Ethane Sulfonic Acid (hepes), Propylene Glycol, Glycolic Acid, PPG-2 Myristyl Ether Propionate, Ethylhexyl Palmitate, PPG-15 Stearyl Ether, Phyllanthus Emblica Fruit Extract, Isopropyl Palmitate, Isostearyl Neopentanoate, Cetearyl Alcohol, PEG-75 Stearate, Glyceryl Stearate, Cetyl Alcohol, Dimethicone, Ammonium Hydroxide, Ceteth-20, Argilla/Magnesum Aluminum Silicate, Tocopheryl Acetate, Steareth-20, Methylparaben, Xanthum Gum, BHT, Citrus Grandis Extract/Grapefruit Extract, CI 19140/Yellow 5, CI 42090/Blue 1, CI 14700/Red 4, Citric Acid

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Isn't there some evidence of phototoxicity in hepes-containing culture mediums?  (see  " Analysis of the cytotoxic effects of light-exposed HEPES-containing culture medium" by Zigler JS, Lepe-Zuniga JL, Vistica B, Gery I (May 1985) and " Phototoxicity of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered culture media for human leukemic cell lines" by Spierenburg GT, Oerlemans FT, van Laarhoven JP, de Bruyn CH (May 1984) )  Where the cytotoxicity is caused by the production of hydrogen peroxide (which is toxic to human cells)?

As I am not a biologist, I can't analyse what effect if any it would have on skin, and I have no idea how the concentration in this treatment compare with the concentration of hepes in culture mediums (which seem to be given in millimoles).  But I am curious about it.

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