walnut oil. Emollient, nonfragrant plant oil. See natural moisturizing factor (NMF).

walnut-shell powder. Abrasive used in scrub products; not preferred to polyethylene beads.

water. The most widely used cosmetic ingredient; water is almost always listed first on an ingredient label because it is usually the ingredient with the highest concentration. Yet, despite claims of the skin’s need for hydration and the claims regarding special types of water used, it turns out that water may not be an important ingredient for skin. Only a 10% concentration of water in the outer layer of skin is necessary for softness and pliability in this part of the epidermis (Source: Skin Pharmacology and Applied Skin Physiology, November-December 1999, pages 344–351). Studies that have compared the water content of dry skin to that of normal or oily skin do not find a statistically significant difference in moisture levels between them (Source: Journal of Cosmetic Chemistry, September/October 1993, page 249). Further, too much water in the skin can be a problem because it can disrupt the skin’s intercellular matrix, the substances that keep skin cells bonded to each other (Source: Contact Dermatitis, December 1999, pages 311–314). The most significant aspect of the skin’s health is the structural organization of the intercellular lipids and the related materials that keep skin intact and prevent water loss (Sources: Trends in Cell Biology, August 2002, page 355; and Journal of the American Academy of Dermatology, August 2002, pages 198–208). See natural moisturizing factor (NMF).

water-binding agent. Wide range of ingredients that help skin retain water (moisture). Glycerin is one of the more typical and effective water-binding agents used in cosmetics. One group of water-binding agents can mimic the skin’s actual structure and can be of benefit in a formulation; these include ceramide, lecithin, glycerin, polysaccharides, hyaluronic acid, sodium hyaluronate, mucopolysaccharides, sodium PCA, collagen, elastin, proteins, amino acids, cholesterol, glucose, sucrose, fructose, glycogen, phospholipids, glycosphingolipids, and glycosaminoglycans. No single one of these is preferred over another because even though they are all effective, none of them can permanently change the actual structure of skin. See natural moisturizing factor (NMF).

watercress extract. There is a small amount of research showing that dietary intake of watercress can inhibit the proliferation of breast and other cancer cells (Sources: Journal of Applied Pharmacology, December 2005, pages 105–113; and Expert Opinion on Pharmacotherapy, December 2004, pages 2485–2501). Research also indicates that watercress extracts can have antioxidant activity, but that information is limited (Source: Applied Biochemistry and Microbiology, July 2001, pages 392–399). However, it is important to note that this research was carried out either in vitro or as animal experiments, definitely not in skin-care products.

wheat germ glycerides. Used as emollient and thickening agents in cosmetics. See glyceryl ester and natural moisturizing factor (NMF).

wheat germ oil. Emollient plant oil similar to all nonfragrant plant oils. See natural moisturizing factor (NMF).

wheat protein. See natural moisturizing factor (NMF) and protein.

whey. Milk contains two primary proteins, casein and whey. When cheese is produced these more liquid components, whey and casein, are separated from the cheese. When eaten or taken in oral supplements, whey protein can have significant antioxidant properties (Source: Journal of Dairy Science, December 2001, pages 2577–2583) as well as anticancer properties (Source: Anticancer Research, November–December 2000, pages 4785–4792) because it generates the production of glutathione in the body, which is a significant antioxidant. Whether or not any of those benefits translate into benefit for skin is unknown. In skin-care products it is most likely a good water-binding agent.

white nettle. Contains components that can have both anti-irritant as well as inflammatory properties (Source: http://www.bastyr.org/academic/botmed/herbs.asp?HerbId=5).

white oak bark extract. See oak root extract.

white tea leaf extract. Extract from the minimally processed buds and leaves of green tea. There is research showing that white and green teas have the highest concentration of antioxidant properties (via their polyphenol and flavonoid content) of all teas, and several in vitro and animal studies have shown that green tea and white tea have anticancer and antimutagenic properties. However, even though tea flavonoids are effective antioxidants, it is unclear to what extent they increase the antioxidant capacity of humans, and there is no research showing what their activity means for skin. It appears that white and green teas have similar amounts of the polyphenol epigallocatechin-3-gallate (EGCG), which is the main antioxidant in tea. The conclusion to be drawn is that white and green tea have nearly identical antioxidant activity (Source: Biochemical and Biophysical Research Communications, volume 296, issue 3, August 23, 2002, pages 584–588.) See green tea.

white willow. See willow bark.

wild ginger. See ginger extract.

wild yam extract. The roots of wild yams were used in the first commercial production of oral contraceptives, topical hormones, androgens, estrogens, progesterones, and other sex hormones. Diosgenin, a component of wild yam, is promoted as a natural precursor to dehydroepiandrosterone (DHEA). Some wild yam products are promoted as “natural DHEA.” Although diosgenin can be converted to steroidal compounds, including DHEA, in the laboratory, this chemical synthesis does not occur in the human body. So taking wild yam extracts orally will not increase DHEA levels in humans (Source: http://www.naturaldatabase.com). There is no research showing that wild yam has any effectiveness when applied topically on skin. If anything, the studies that do exist demonstrate that topical application of wild yam has little to no effect on menopausal symptoms (Source: Climacteric, June 2001, pages 144–150). See DHEA.

willow bark. Contains salicin, a substance that when taken orally is converted by the digestive process to salicylic acid (beta hydroxy acid). The process of converting the salicin in willow bark to salicylic acid requires the presence of enzymes, and is complex. Further, salicin, much like salicylic acid, is stable only under acidic conditions. The likelihood that willow bark in the tiny amount used in cosmetics can mimic the effectiveness of salicylic acid is at best questionable, and in all likelihood impossible. However, willow bark may indeed have some anti-inflammatory benefits for skin because, in this form, it appears to retain more of its aspirin-like composition.

willow herb. See Epilobium angustifolium extract.

wintergreen oil. Can be very irritating and sensitizing (Source: http://www.naturaldatabase.com). See counter-irritant.

witch hazel. Can have potent antioxidant properties (Sources: Phytotherapy Research, June 2002, pages 364–367; and Journal of Dermatological Science, July 1995, pages 25–34) and some anti-irritant properties (Source: Skin Pharmacology and Applied Skin Physiology, March-April 2002, pages 125–132). However, according to the Consumer’s Dictionary of Cosmetic Ingredients (Sixth Edition, Ruth Winter, 2005, Three Rivers Press), “Witch hazel has an ethanol [alcohol] content of 70 to 80 percent and a tannin content of 2 to 9 percent. Witch hazel water … contains 15% ethanol.” The alcohol can be an irritant. Witch hazel’s high tannin content (and tannin is a potent antioxidant), can also be irritating when used repeatedly on skin, although when used for initial swelling from burns it can reduce inflammation. See tannin.