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Developed in Paris, and available in 40 countries worldwide, Biologique Recherche Exfoliators ($55.00 for 5.1 fl.oz, $87.00 for 8.5 fl.oz., BiologiqueRecherche.com) are popular and luxurious twice-daily treatments for the skin.  Containing usnic acid, lactic acid, witch hazel, onion extract, and sage extract, Biologique Recherche Exfoliators promise to “purify, hydrate, tone, control sebum” and “balance the skin,” whether the formulation in question is designed for thicker skin (P50), thinner/sensitive skin (P50V) or mature and very sensitive skin (P50W).
The main ingredient, usnic acid, is relatively rare in cosmetic formulations.  Derived from lichen plants, usnic acid is more commonly developed as an antibiotic, but provides anti-inflammatory effects for the skin.  According to a 2002 German review in Naturwissenschaften, usnic acid is effective in preventing inflammation and ultraviolet absorption in the skin, but more studies need to be done to determine the true efficacy of the ingredient in treating acne, rosacea, and other inflammation-related skin ailments.  Further, a 2006 study in Contact Dermatitis reports that some patients may have an allergic reaction (contact dermatitis) with continued usnic acid exposure.  In the study, 30 of 164 lichen pickers in a small community in northern Finland were found to develop dermatitis.  While 9 of these patients had allergic contact reactions, usnic acid could only be identified as the cause in 3 of the patients’ allergic contact reactions. Â
Another ingredient in Biologique Recherche Exfoliators, lactic acid, is a well-established alpha hydroxy acid (AHA) used to treat dry skin.  In fact, arguably the most popular source of lactic acid is prescription LacHydrin, which has been FDA approved to treat dry skin.  For anti-aging treatments, glycolic acid is usually preferred to lactic acid because it has a smaller molecular structure, which allows it to easily and efficiently penetrate the skin, and also because glycolic acid increases the thickness and firmness of the skin, while lactic acid does not.  So why does Biologique Recherche (and some other anti-aging products) contain lactic acid as the AHA?  According to the British Journal of Dermatology, amongst other sources, lactic acid is less irritating and results in less transepidermal water loss than glycolic acid and other forms of AHAs, making it the preferred choice for some skin care formulations.
Like usnic acid, research on the effects of witch hazel, onion extract, and sage extract on human skin is limited.  Witch hazel is soothing according to a study in Archives of Dermatology; onion extract is declared effective for scars in Dermatologic Surgery; lastly, sage extract is declared to have some antioxidant activity in the journal BioFactors.  Unfortunately, the benefits of these natural ingredients for the skin are less well-established than, say, retinol, niacinamide, or certain peptides.  As such, they’re probably not a great reason to buy the product.
So why do I like Biologique Recherche Exfoliators?  Honestly, it’s all anecdotal evidence:  it feels soothing and cooling on the skin; I swear it has helped my moisturizer drink in better; the packaging is beautiful.  However, despite my natural inclination to say, “I love it, buy it!”, careful examination reveals that the science behind the ingredients just isn’t there, much as I would like it to be.  With that said, this product’s presentation and luxurious feel makes it a delightful indulgence (and an amazing gift), but as far as providing solid daily sustenance for the skin, you just might want to look elsewhere.  Product Rating: 6.0/10.0 (High concentration of proven effective ingredients: 1.5/3.0, for high lactic acid concentration.  New technology or unique formulation: 2.0/3.0, as it is unique.  Value for the money: 1.5/3.0.   Sunscreen: N/A for an exfoliator, bonus point, 1.0/1.0)  .