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Spice up Your Formulation: Addressing Issues Caused by Acids in Skin Care Products
By: Zolt Szabados, Technical Services Manager, BASF Corporation
Posted: July 24, 2009
One of the greatest challenges every formulator faces is to create the most amazing product, with the best activity, that can improve skin aesthetics significantly and has the best feel and appearance. There are several antiaging ingredients on the market that help rejuvenate the skin; however, in many cases, they affect the appearance and the feel of the product they’re formulated into. Alpha- and beta-hydroxy acid products are an example. Alpha hydroxy acids (glycolic acid, lactic acid, etc.), even at low concentration, have the ability to reduce cell adhesion in the top layer of the skin, that promotes exfoliation of the outermost layer and leads to a smoother, healthier looking skin. They are widely and effectively used in the treatment of photo-damaged skin, wrinkling and acne; however, it has been difficult to formulate products that really have a great appearance and feel using these acids because of the required low pH (pH= 3-4) where these acids function.
Most of the rheology modifiers that offer great emulsion stability, excellent feel and esthetics where based on polyacrylate derivatives, which need to be neutralized (pH > 5.5) in order to work. Other antiaging ingredients that improve the moisture content of the skin, which plays a major role in maintaining skins’ youthful and healthy appearance, are a combination of several extracts, dispersed in a base that may contain electrolytes, or are salts themselves, such as sodium ascorbyl phosphate. These ingredients often negatively influence the performance and thickening capacity of polyacrylates.
In order to improve the stability, many formulators have resorted to various combinations of thickeners that resulted in undesired textures, greatly affecting the feel and discouraged consumers in using these preparations. Ingredients such as Luvigel STAR have been created to address these issues. A thickener that can work in any skin care application,Luvigel STAR’s thickening capacity does not depend on ionic bonding like in the case of polyacrylic acid based thickeners, but on interactions of the hydrophobic ingredients of the emulsion, especially the emulsifying system. These advances allow greater versatility in formulating. Comparisons new rheology modifiers and several commercially available products demonstrate the new ingredients' superiority in effectively thickening formulations containing high concentrations of electrolytes.