N6-furfuryladenine. Technical name for kinetin. See kinetin.

N-acetyl-L tyrosine. See tyrosine.

NaPCA. See natural moisturizing factor (NMF) and sodium PCA.

Narcissus poeticus wax. Fragrant flower extract that can cause irritation and dermatitis (Source: http://www.naturaldatabase.com).

Nardostachys jatamansi. See spikenard.

Nasturtium officinale extract. See watercress extract.

natto gum. Fermentation product of soy protein. It may be a potent antioxidant (Source: Journal of Agricultural Food Chemistry, June 2002, pages 3592–3596).

natural ingredient. The FDA has tried to establish official definitions and guidelines for the use of certain terms such as natural and hypoallergenic, but its regulations were overturned in court. That means that cosmetics companies can use these terms on ingredient labels to mean anything they want, with the result that they almost always mean nothing at all. The term all-natural has considerable market value in promoting cosmetic products to consumers, but a close look at an ingredient label reveals that plant extracts make up only a small percentage of the product. Plus, when a plant is added to a cosmetic, preserved, and stabilized with other ingredients, it loses its natural qualities (Source: FDA Consumer Magazine, May–June 1998, revised May 1998 and August 2000).

natural moisturizing factor (NMF). One of the primary elements in keeping skin healthy is making sure the structure of the epidermis (outer layer of skin) is intact. The components that do this are often called natural moisturizing factor (NMF) or ingredients that mimic the structure and function of healthy skin. While the oil and fat components of skin prevent evaporation and provide lubrication to the surface of skin, it is actually the intercellular matrix, along with the skin’s lipid content, that gives skin a good deal of its surface texture and feel.

The intercellular matrix is the skin’s first line of defense against water loss. When the lipid and NMF content of skin is reduced, we experience surface roughness, flaking, fine lines, and a tight, uncomfortable feeling. The longer the skin’s surface layer (stratum corneum) is impaired, the less effective the skin’s intercellular matrix becomes (Sources: Skin Research and Technology, August 2000, pages 128–134; and Dermatologic Therapy, 2004, volume 17, Supplement 1, pages 43–48). Moreover, the skin’s healing process is impaired. NMFs make up an expansive group of ingredients that include amino acids, ceramides, hyaluronic acid, cholesterol, fatty acids, triglycerides, phospholipids, glycosphingolipids, urea, linoleic acid, glycosaminoglycans, glycerin, mucopolysaccharide, and sodium PCA (pyrrolidone carboxylic acid). Ingredients that mimic the lipid content of skin include apricot oil, canola oil, coconut oil, corn oil, jojoba oil, jojoba wax, lanolin, lecithin, olive oil, safflower oil, sesame oil, shea butter, soybean oil, squalane, and sweet almond oil, all of which can be extremely helpful in making dry skin look and feel better.

All of the skin’s supporting NMFs and lipids are present in the intercellular structure of the epidermis, both between skin cells and in the lipid content on the surface of skin. When any of these ingredients are included in skin-care products, they appear to help stabilize and maintain this complex intercellular-skin matrix. More important, all of these ingredients, and many more, help support the intercellular area of the skin by keeping it intact. This support helps prevent surface irritation from penetrating deeper into the skin, helps keep bacteria out, and aids the skin’s immune/healing system. Using moisturizers of any kind that contain NMFs (whether they are labeled as anti-aging, antiwrinkle, serums, lotions, or sunscreens) allows your skin to do its job of repairing and regenerating itself without the impedances brought on when skin is suffering from dryness, environmental distress, or excess irritation (Sources: Clinical Geriatric Medicine, February 2002, pages 103–120; Progressive Lipid Research, January 2003, pages 1–36; Journal of the European Academy of Dermatology and Venereology, November 2002, pages 587–594; Contact Dermatitis, June 2002, pages 331–338; Journal of Investigative Dermatology, May 1996, pages 1096–1101; British Journal of Dermatology, November 1995, pages 679–685; Skin Pharmacology and Physiology, September–October 2004, pages 207–213; Free Radical Research, April 2002, pages 471–477; and Journal of Lipid Research, May 2002, pages 794–804).

neem extract or oil. Extract from leaves of the neem tree, it has potential toxic effects, although it also has been shown to have antimicrobial properties (Sources: Life Sciences, January 2001, pages 1153–1160; Journal of Ethnopharmacology, August 2000, pages 377–382; Phytotherapy Research, February 1999, pages 81–83; and Mutation Research, June 1998, pages 247–258).

neopentyl glycol dicaprylate/dicaprate. Used as an emollient and thickening agent.

neopentyl glycol diheptanoate. Mixture of neopentyl glycol (film-forming agent and solvent) and heptanoic acid (fatty acid made from grapes), the compound functions as a non-aqueous skin-conditioning agent and thickener.

neroli. See orange blossom.

neroli oil. Fragrant plant oil that can be a skin irritant and sensitizer.

nettle extract. Extract that may have anti-inflammatory properties (Source: Healthnotes Review of Complementary and Integrative Medicine, http://www.healthwell.com/healthnotes/Herb/Nettle.cfm).

niacin. See niacinamide.

niacinamide. Also called vitamin B3, niacin, and nicotinic acid, this water-soluble ingredient is stable in the presence of heat and light. Topical application of niacinamide has been shown to increase ceramide and free fatty acid levels in skin, prevent skin from losing water content, and stimulate microcirculation in the dermis (Sources: British Journal of Dermatology, September 2000, pages 524–531; and Journal of Cosmetic Dermatology, April 2004, page 88). One small study showed that 2% niacinamide was more effective than petrolatum (Vaseline) at reducing water loss from skin and increasing its hydration levels (Source: International Journal of Dermatology, March 2005, pages 197–202). Procter & Gamble, whose Olay skin-care line sells several products with niacinamide, published a double-blind study involving 50 women. The subjects used a product containing 5% niacinamide (whether that amount is included in Olay’s niacinamide products was not mentioned) for a period of 12 weeks. Results included an improvement in the appearance of wrinkles, a decrease in skin discolorations, less redness, a reduction in sallowness, and improved elasticity (Source: Dermatologic Surgery, July 2005, pages 860–865). Another study seconded P&G’s findings that niacinamide is a helpful ingredient for addressing skin discolorations. It appears that topical niacinamide has an inhibitory effect on the transfer of melanosomes to skin cells, thus it interrupts the process that causes irregular pigmentation to form (Source: Experimental Dermatology, July 2005, pages 498–508).

In addition to niacinamide’s growing reputation as an excellent barrier-repair and skin-lightening agent, some animal studies and in vitro studies on human fibroblasts (cells that produce connective tissue such as collagen) demonstrated that niacinamide may have a mitigating effect on skin tumors (Source: Nutrition and Cancer, February 1997, pages 157–162). There are fewer studies that examined niacinamide’s anti-acne properties. An older study that compared a gel containing 4% niacinamide with the prescription acne medicine Clindamycin found that niacinimide works just as well as the prescription, but without the risk of antibiotic resistance (Source: International Journal of Dermatology, June 1995, pages 434–437).

Perhaps even more important is niacinamide’s potential as a cell-communicating ingredient (Sources: Journal of Radiation Research, December 2004, pages 491–495; British Journal of Dermatology, October 2003, page 681; and Journal of Dermatological Science, volume 31, 2003, pages 193–201). See cell-communicating ingredients.

nicotinamide. See niacinamide.

nicotinic acid. See niacinamide.

nitrogen. Used as a propellant in cosmetic products; as nitric oxide, it can generate free-radical damage and cause cell death (Source: Mechanisms of Ageing and Development, April 2002, pages 1007–1019). Topically applied nitrogen in the amounts present in skin-care products has minimal research (and no third-party, substantiated research) establishing its benefit for skin, but it does not appear to be harmful in its pure form.

nonoxynols. Used as mild surfactants. See surfactant.

nordihydroguaiaretic acid. Component of some plants that has been shown to have anticancer properties for skin and that may also protect skin from sun damage; also a potent antioxidant (Sources: British Journal of Cancer, April 2002, pages 1188–1196; Molecular Carcinogenesis, June 2002, pages 102–111; and Biochemical Pharmacology, March 2002, pages 1165–1176).

nylon-12. Powder substance that is used as an absorbent and thickening agent.

Nymphaea tetragona. Also known as pygmy waterlily. The stem has been shown in vitro to be not only a potent antioxidant but also able to inhibit the expression of collagen-depleting MMP-1 when applied to human fibroblast cells (Source: Journal of Cosmetic Science, January/February 2007, pages 19-32). See matrix metalloproteinases.