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Cosmetic Chemistry and the Esthetician
By: Ivana Veljkovic, PhD
Posted: September 24, 2010, from the October 2010 issue of Skin Inc. magazine.
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Suspensions are usually in liquid form and separation of a suspension’s ingredients is typical. Agitating the bottle is necessary to redistribute the ingredients throughout the product, ensuring the active ingredients penetrate into the skin properly. Suspensions are used when a product’s ingredients will not dissolve when mixed with oil or water. Many times, cleansers will be suspensions. A gel base is commonly used in serum products. Gels are transparent, semi-liquids that are either completely water-soluble or completely oil-soluble. Gels are thinner and typically penetrate easier than emulsions, making them the more common vehicle for corrective products.
Stable and effective
Stability pertains to two important aspects of a product: the breakdown of its active ingredients and the prevention of abnormal microbial growth. Some think of preservatives as a negative; in fact, preservatives protect the product and the consumer by preventing the growth of harmful bacteria, yeast and mold. In actuality, all products that contain water must have some type of preservative system in place. Certain multifunctional ingredients offer preservative properties as well as other benefits, allowing for misleading “preservative-free” claims.
If a product breaks down, or oxidizes, it loses efficacy. Oxidation involves the altering of an ingredient’s molecule. In some cases, this alteration is beneficial. For example, the conversion of retinol into retinoic acid in the skin involves oxidation of the retinol molecule. This type of oxidation must be assisted by certain enzymes and occur within the skin, not in the bottle, in order to make it effective. Oxidation is negative when a product oxidizes before it is able to interact with the skin. The most obvious indication of product oxidation is the darkening in color throughout time. Many of the most effective topical ingredients, including retinoids, L-ascorbic acid and several sunscreen agents, are inherently unstable and prone to oxidation. Oxidation typically occurs when a fragile ingredient comes in contact with air, water or light. Special steps must be made to ensure products that contain unstable ingredients are able to maintain their stability and functionality.
Esterfication. This process involves the binding of one molecule to another. Ester molecules can be effective; however, the skin must be able to break apart the ester and free the actual active ingredient. One example of an esterfied molecule is tocopheryl acetate, which is a form of vitamin E. Tocopheryl acetate combines tocopherol (vitamin E) with acetic acid, making a more stable molecule. Once applied to the skin, the molecule cleaves, freeing the tocopherol to provide its potent antioxidant effects. Another example is ascorbyl palmitate, which combines L-ascorbic acid with palmitic acid. Although this seems like a logical way to stabilize the active L-ascorbic acid, the skin lacks the mechanism to free the L-ascorbic acid; therefore, these esters do not provide all of its topical benefits.
Encapsulation. This is a protective casing that shields the active ingredient from contact with air, water or light. This method of stabilization is widely considered the most effective, as the ingredient is still in its most active form. The casings are easily broken upon manipulation or contact with skin, thereby releasing the active ingredient.