No. 13, July 2005 Somerset Cosmetic Company PO Box 3372 Renton, WA 98056 omemade osmetics www.makingcosmetics.com

streaking which is often seen in this product type. Moisturizers & Hum ectants Their relatively high cost has limited their usage. Traditionally, moisturization was believed to inhibit Humectants MP Diol: MP diol has properties similar to hexylene transepidermal water loss by occlusion. Water Humectants attract water when applied to the skin and butylene glycol but is less expensive (similar to originates in the deeper epidermal layers and and theoretically improve hydration of the stratum propylene glycol). moves upward to hydrate cells in the upper layer corneum. However, the water that is drawn to the It is of note that all glycol-type humectants can of the skin (stratum corneum), eventually being skin is transepidermal water, not atmospheric additionally improve the effect of preservatives lost to evaporation. Research suggests that the water. Continued evaporation from the skin can (e.g. paraben) since they take away the water stratum corneum acts an active membrane actually exacerbate dryness. from the bacteria (needed for their growth) and consisting of intercellular lipids (i.e. ceramides, Chemically, all humectants have something in improve the solubility of parabens. cholesterol and fatty acids), thereby forming a common: hydroxyl groups. These groups allow Urea & alpha-hydroxy acids (AHAs): In addition to water-barrier function. In addition, the stratum them to partake in the association process known their humectant properties, urea and AHAs (e.g. corneum contains a natural mixture of amino acids, as hydrogen binding. In other words: they attract lactic acid) are keratolytic. Urea is a humectant in lactates, urea and electrolytes, which also help water (latin: humectare = moisten). lower concentrations (10%), but in higher retain water. Humectants include glycerin, sorbitol, propylene concentrations (20-30%) it is mildly keratolytic by Dry skin is noted when the moisture content is less glycol, hexylene and butylene glycol, MP Diol, disrupting hydrogen bonds or epidermal proteins. than 10%, and there is loss of continuity of the urea, alpha hydroxy acids (i.e., lactic acid) and AHAs, such as lactic acid or glycolic acid, appear to stratum corneum. Scientifically, the moisturizing other sugars. increase cohesion of the stratum corneum cells, treatment involves a 4-step process: Glycerin: glycerin is by fare the most popular of all thereby reducing roughness and scaling. humectants used in personal care products. While 4 Steps of Moisturizing Treatment it is a very good compound when it comes to Emollients and Proteins Emollients smooth skin by filling spaces between Repairing the skin barrier moisturization, and its natural connotation is a real Increasing water content positive, when used at concentrations above 5% it skin flakes with droplets of oil, and are not usually Reducing transepidermal water loss can leave the skin with a sticky, unpleasant feel. occlusive unless applied heavily. When combined Restoring the lipids water barrier function Sorbitol: Sorbitol, available as powder or a 70% with an emulsifier, they may help hold oil and water aqueous solution, is typically used in toothpastes in the stratum corneum. Examples of emollients Occlusives and many other personal care products. include mineral oil, lanolin, fatty acids, cholesterol, Occlusives are substances that physically block Propylene Glycol: propylene glycol is less commonly squalene, and structural lipids. transepidermal water loss in the stratum corneum. seen in personal care products. While it is less Fatty acids: fatty acids and fatty alcohols exert Petrolatum in a minimum concentration of 5% is sticky than glycerin, there have been concerns their benefits through effects on the skin barrier. the most effective occlusive followed by lanolin, regarding its safety when used at high concentra- Examples include stearic, linoleic, linolenic, oleic, mineral oil, and silicones such as dimethicone. tions above 7.5%. and lauric acids, which can be found, for example, Petrolatum is widely used as a classic moisturizer. Hexylene and Butylene Glycol: both compounds in palm oil, coconut oil, and grapeseed oil. Lanolin is also widely used and quite effective are often used in emulsions designed for facial Ceramides: Structural lipids as ceramides which are although it has been shown to induce contact applications due to their non-sticky skin feel. When located between skin cells, are also felt to play a dermatitis in some cases. employed in makeup emulsions, they can reduce considerable role in the water-holding potential of the stratum corneum. Ceramide is a major skin cell Moisturizing Compounds and thier Mode of Action component and plays a major role in generating multilamellae architecture. Natural ceramides Class Mode of Action Compounds Comments themselves are at present too expensive to make Occlusives Physically block transepi- Petrolatum, lanolin, mineral oil, May be comedogenic, commercially available. However, synthetic dermal water loss silicones, zinc oxide contact dermatitis (lanolin) ceramides (e.g. lacto-ceramide encapsulated in liposomes) are now available and have been Humectants Attract water to stratum Glycerin, propylene glycol, May be irritant at high clinically shown to be effective in preventing and corneum sorbitol, hexylene glycol, concentrations (AHAs), improving dry skin. butylene glycol, urea, alpha- Glycols also increase effect Proteins: like emollients, protein shrink on the skin hydroxy acids (AHAs) of preservatives leaving a film that smoothes the skin, stretches out some of the fine wrinkles, and avoids water loss. Emollients Smooth skin by filling Plant oils, polyisobutene, spaces between skin flakes squalene, fatty acids, ceramide Sources: with droplets of oil (e.g. lacto-ceramide) Klein K. Humectants: more than meets the eye (or skin). Cosmetics & Toiletries 2005; 120(2): 30 Lynde CW. Moisturizers: what they are and how they Proteins Replenish proteins in Collagen, keratin, elastin, work. Skin Therapy Letters 2001; 6(13): 3 stratum corneum protein mixtures (e.g. wheat protein) T. Bombeli, MD

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