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Skin Care Moisturizers
By: Eric S. Abrutyn, TPC2 Advisors Ltd., Inc.
Posted: November 30, 2010, from the December 2010 issue of Cosmetics & Toiletries.
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Another popular hydrocarbon emollient that is used as a moisturizer is petrolatum. It is based on linear and branched aliphatic and aromatic chain hydrocarbons and waxes. A sub-class of hydrocarbons is isoparaffins—aliphatic branched chain hydrocarbons of high purity; e.g. isoeiconsane, isohexadecane, etc. There is a variety of pure and blended hydrocarbons with carbon chain lengths greater than 10 that provide excellent emolliency to both skin and hair.
Fatty acid derivatives are generally sourced from triglycerides and waxes, and can also be made synthetically. The most popular carbon chain length fatty acids are C12-22, as well as unsaturated C18 fatty acids, but there are a number of examples using C3-8. Common derivatives used as emollients are: esters of mono and polyhydric alcohols, both linear and branched, which were first developed in the 1950s as porosity esters to duplicate properties of the NMF;9, 10 dicarboxylic and tricarboxylic acid derivatives such as esters; carbohydrate derivatives including starch; and methylsiloxane derivatives (see Figure 2).
Popular carbohydrates used as emollients are sucrose, glucose and methylglucoside esters, which were first developed in the early 1970s. In addition, polymers such as polyesters, polyethers, polyacrylates and others are used extensively as emollients and film-forming moisturizers. Finally, ethers and carbonates are finding acceptable application as emollients in skin and hair applications.
Objective Skin Moisture Assessments
It is important for product developers to understand how to measure11 skin moisturization so as to determine whether the functional component of a formula is acting as a moisturizer, humectant or emollient. There is a critical balance between clinical measurements and the consumer’s perception of performance. By most accounts, consumers make an initial assessment of a moisturizer’s performance based on how the product applies to their skin, in addition to perceptions later in the day of relief from dry skin symptoms. Consumers will continue to use a product if their symptoms are continually reduced and healthier skin is maintained longer, ideally greater than 24 hr.
Clinical evaluations can assess the ability of a formula to alleviate dry skin symptoms within a reasonable and acceptable time frame. The basic methods to assess clinical dry skin and skin hydration include TEWL, conductance, corneometry, dryness and desquamatry.