macadamia nut oil. Used in cosmetics as an emollient for dry skin.

Mad cow disease. Technically known as bovine spongiform encephalopathy, or BSE, mad cow disease is a chronic degenerative disease affecting the central nervous system of cattle. The concern for humans is the risk of eating meat or meat products that contain the BSE pathogen. Whether bovine-derived ingredients used in cosmetics can harbor the disease and cause health risks is unknown, but theoretically there is a remote possible risk. Some researchers believe that there is no evidence BSE can be contracted through the skin (Source: Cosmetic Dermatology, December 2001, pages 43–47); however, neither cooking nor preserving nor any of the other processing that most cosmetics go through can eliminate BSE pathogens. That means that if animal by-products are used in cosmetics (in particular bovine placenta and spleen extracts), they can pose a risk, albeit remote, to the user. The British BSE Committee (http://www.bse.org.uk/), in various reports, has mentioned a concern that people could become infected if the creams are used on broken skin.

It is important to realize that very few products contain those kinds of ingredients. If you are thinking of buying cosmetics that contain animal organ extracts of any kind, you may want to reconsider, or discard them if you have already made a purchase.

magnesium. Earth mineral that has strong absorbent properties and some disinfecting properties. Magnesium obtained via diet or oral supplements is essential for maintaining health.

magnesium aluminum silicate. Powdery, dry-feeling, white solid that is used as a thickening agent and powder in cosmetics.

magnesium ascorbyl palmitate. Stable derivative of vitamin C that can be an effective antioxidant. See vitamin C.

magnesium ascorbyl phosphate. Form of vitamin C that is considered stable and an effective antioxidant for skin (Sources: Photochemistry and Photobiology, June 1998, pages 669–675; and Journal of Pharmaceutical and Biomedical Analysis, March 1997, pages 795–801). For skin lightening, there is only a single study showing it to be effective for inhibiting melanin production (Source: Journal of the American Academy of Dermatology, January 1996, pages 29–33). The study concluded that a moisturizer with a 10% concentration of magnesium ascorbyl phosphate “suppressed melanin formation…. The lightening effect was significant in 19 of 34 patients with chloasma or senile freckles and in 3 of 25 patients with normal skin.” One study is not exactly anything to write home about, not to mention that at present there are no products on the market that contain 10% magnesium ascorbyl phosphate.

magnesium carbonate. Inorganic mineral salt used as an absorbent, opacifying agent, coloring agent, or to adjust the pH of cosmetic products.

magnesium gluconate. Magnesium is an essential mineral the body uses to maintain circulatory and nervous system function. There is a small amount of research showing that it has antibacterial properties (Sources: Bulletin of Experimental Biology and Medicine, February 2001, pages 132–135; and Journal of Pharmacy and Pharmacology, May 1998, pages 445–452). There is also research showing it may be helpful for healing burns.

magnesium hydroxide. Active ingredient in milk of magnesia. It is an absorbent and has antibacterial properties for skin.

magnesium laureth sulfate. Mild detergent cleansing agent. See surfactant.

magnesium oleth sulfate. Mild detergent cleansing agent. See surfactant.

magnesium stearate. Used as a thickening agent in cosmetics.

magnesium sulfate. Commonly known as Epsom salt, a magnesium salt used as a thickening agent.

malic acid. See AHA.

mallow. Can be used as a thickening agent in cosmetics and may have anti-inflammatory and soothing properties for skin due to its content of mucilage, flavonoids, and anthocyanidins (Source: Healthnotes Review of Complementary and Integrative Medicine, http://www.healthwell.com/healthnotes/Herb/Mallow.cfm).

Malva sylvestris extract. Extract from the blue mallow flower, it may have some anti-inflammatory and soothing properties for the skin, as well as some potential antioxidant benefits (Sources: http://www.naturaldatebase.com; International Journal of Food Sciences and Nutrition, February 2004, pages 67–74; and Journal of Ethnopharmacology, January 2004, pages 135–143).

Malvaceae extract. Extract from plants of the Malvaceae family, which includes over 1,000 species, found in tropical and temperate regions the world over. Their varying benefits and problems are diverse. Consequently, if “Malvaceae” is present on a cosmetic ingredient label, it is misleading, because each of the 1,000 species has its own pros and cons.

mandarin orange oil or extract. Primarily used as a fragrance; it can be a skin irritant. There is no research showing it has any benefit when applied topically.

mandelic acid. Alpha hydroxy acid, also known as amygdalic acid. There is scant research showing this to be an effective alternative to other AHAs, though it does have germicidal activity. Unlike glycolic acid, mandelic acid is light-sensitive and should be packaged in an opaque container (Source: Handbook of Cosmetic and Personal Care Additives, Second Edition, volume 2, Synapse Information Resources, 2002).

manganese gluconate. Mineral found in trace amounts in tissues of the body. While manganese plays a vital role in the processes of many body systems, there is no evidence it serves any purpose topically on skin, though it may act as an antioxidant.

manganese violet. Coloring agent/additive permanently listed (as of 1976) by the FDA for use in cosmetic products, including those designed for use around the eye.

Mangifera indica root. Extract derived from the mango tree; it can have antioxidant properties (Source: Journal of Agricultural Food Chemistry, February 2002, pages 762–766).

manuka oil. Extract derived from the New Zealand tea tree; the oil is similar to that of the Australian tea tree, Melaleuca alternifolia. Manuka oil has antifungal and antibacterial properties (Sources: Phytotherapy Research, December 2000, pages 623–629; and Pharmazie International Journal of Pharmaceutical Sciences, June 1999, pages 460–463). See tea tree oil.

marigold. See calendula extract.

marionberry. Fruit that has potent antioxidant properties (Source: Journal of Agricultural Food Chemistry, June 5, 2002, pages 3495–3500).

marjoram. Herb with a fragrant component used in cosmetics; can be a skin irritant.

marshmallow. See mallow.

Mastocarpus stellatus. See algae.

mate extract. See yerba mate extract.

Matricaria oil. See chamomile.

matrix metalloproteinases. Also called MMPs, a group of 23 different enzymes that cause substances in the body to break down. Of the 23 types, MMP-1, also known as collagenase, is responsible for the destruction of collagen. Generated primarily by unprotected sun exposure and the aging process, it is also present in sebum (which may be a cause of acne) (Sources: Journal of Investigative Dermatology, October 2005, pages 673–684; Photochemistry and Photobiology, October 2003, pages 355–360; and Photodermatology, Photoimmunology, and Photomedicine, April 2001, pages 178–183).

One of the primary ways to decrease MMPs in skin, particularly MMP-1 is smart sun behavior and use of well-formulated sunscreens. There is also research showing that epigallocatechin-3-gallate (a derivative of green tea), retinoic acid (RA), eicosapentaenoic acid (an omega-3 fatty acid), beta-carotene, DHEA (though this is controversial), polysaccharides, vitamin E, and vitamin C, and flavonoids, to name a few, can inhibit MMPs and increase TIMPs (tissue inhibitors of metalloproteinases; when TIMPs increase in skin, MMPs decrease).

MEA. Abbreviation for monoethanolamine. See alkyloamides and triethanolamine.

meadowsweet extract. Extract that can have anti-inflammatory properties (Source: Journal of Agricultural Food Chemistry, October 1999, pages 3954–3962).

Medicago sativa. See alfalfa extract.

Melaleuca alternifolia. See tea tree oil.

Melaleuca cajeputi oil. There is no research showing that this oil, which is derived from a plant in the same family as the plant that is the source of tea tree oil, has any antibacterial properties. It may cause skin irritation (Source: The Illustrated Encyclopedia of Essential Oils, Rockport, MA, Element Books, 1995, page 170).

melasma. Melasma or chloasma are brownish discolorations of the face, hands, chest, and neck. Pregnancy is a common cause of melasma, as well as taking oral contraceptives. However, unprotected exposure to sunlight is also a major cause.

Melia azadirachta. See neem extract or oil.

melibiose. Saccharide that can have good water-binding properties. See mucopolysaccharide and natural moisturizing factor (NMF).

Melissa officinalis. See balm mint extract and counter-irritant.

Mentha arvensis. See cornmint.

Mentha piperita. See counter-irritant and peppermint.

Mentha spicata. See counter-irritant and spearmint oil.

Mentha viridis. See counter-irritant and spearmint oil.

menthol. Derived from peppermint; menthol can have the same irritating effect as peppermint on skin (Source: Archives of Dermatologic Research, May 1996, pages 245–248). See counter-irritant and peppermint.

menthone. Major constituent of peppermint. See peppermint.

menthoxypropanediol. Synthetic derivative of menthol. It is known to produce effects that are twice as strong as menthol, which makes it doubly irritating for skin or lips. Menthoxypropanediol is most often used in lip-plumping products (Source: http://www.leffingwell.com/cooler_than_menthol.htm). See menthol.

menthyl lactate. Used as a cooling agent and fragrance in cosmetics. It is a derivative of menthol and is supposed to be less irritating than menthol. See counter-irritant and menthol.

methanol. See alcohol.

methionine. See amino acid and antioxidant.

methyl gluceth-20. Liquid that functions as a water-binding and skin-conditioning agent.

methylchloroisothiazolinone. In combination with methylisothiazolinone, it goes by the trade name Kathon CG. Introduced into cosmetics in the mid-1970s, it elicited a great number of sensitizations in consumers. This led to it not being included in cosmetics other than rinse-off products (Sources: Contact Dermatitis, November 2001, pages 257–264; and European Journal of Dermatology, March 1999, pages 144–160).

methyldibromo glutaronitrile. Formaldehyde-releasing preservative (Source: Contact Dermatitis, December 2000, pages 339–343). See formaldehyde-releasing preservative.

methyldihydrojasmonate. Synthetic fragrant component.

methyleugenol. Natural constituent of plant oils such as those from rose, basil, blackberry, cinnamon, and anise. According to the November 9, 1998, issue of The Rose Sheet (an insider cosmetics industry newsletter), the National Toxicology Program Board of Scientific Counselors concluded that “methyleugenol, a component of a number of essential oils, has shown clear evidence of carcinogenic activity in male and female rats and mice.” The study is an animal model and so the results may or may not be applicable to humans.

methylisothiazolinone. Preservative that should be used only in rinse-off products because it can be too irritating when left on skin. See methylchloroisothiazolinone and preservatives.

methylparaben. See parabens.

methylpropanediol. Glycol that functions as a solvent. Methylpropanediol can enhance the penetration of ingredients (such as salicylic acid) into the skin.

methylsilanol mannuronate. See silicone.

methylsilanol PEG-7 glyceryl cocoate. A glyceryl ester used as an emollient and thickening agent in cosmetics. See glyceryl ester and silicone.

methylsufonylsulfate. See antioxidant.

methylsulfonylmethane. Also known as MSM. There is no published research to back up claims made about any benefit this sulfur compound may have for arthritis or other physical ailments. There is no research about its effect when applied topically. Sulfur is stored in every cell of the body, particularly in the hair, nails, and connective tissue of joints and skin, where it is an important structural protein component. An MSM manufacturer sponsored two very small trials, but the results have not been published. Until additional research is published, MSM enthusiasm should be tempered. MSM is available in capsules and powder for oral intake or in creams for topical use. To date, there have been no reports of toxicity (Sources: Harvard Health Letter, August 2000, http://www.health.harvard.edu; Healthnotes Review of Complementary and Integrative Medicine, http://www.healthwell.com/healthnotes/herb; and http://www.drweil.com).

Mexoryl SX. Also called ecamsule (technical name terephthalylidine dicamphor sulfonic acid), Mexoryl SX is a synthetic sunscreen agent developed and patented by L’Oreal and used in the company’s sunscreen products sold outside the United States since 1993 (first approved for use in Europe in 1991). In July 2006, the FDA approved the use of Mexoryl SX in the United States, but only in a single sunscreen product, La Roche-Posay’s Anthelios SX SPF 15 (L’Oreal owns La Roche-Posay). The FDA did not approve Mexoryl SX for use in any other sunscreen; only in that one specific product. Anthelios SX will list Mexoryl SX as ecamsule on the label along with the other actives avobenzone and octocrylene (both of these sunscreen ingredients have been approved for use in the United States for years).

L’Oreal blitzed the media with press releases about this approval, touting Mexoryl SX’s improved stability when compared with avobenzone, or intimating that it is the best UVA sunscreen available. According to sunscreen expert Ken Klein, president of Cosmetech Labs, who also teaches sunscreen formulation classes for the Society of Cosmetic Chemists, although Mexoryl SX does not degrade after hours of sun exposure at the same rate as avobenzone, it does indeed break down, losing 40% of its protective properties. Studies have shown that after controlled doses of UV exposure, avobenzone breaks down at a rate of 65%, so Mexoryl SX does have a slight stability edge. However, avobenzone can be made more stable by combining it with other active ingredients, specifically octocrylene (Source: International Journal of Pharmaceutics, January 13, 2006, pages 123–128). Outside the United States, Tinosorb (another sunscreen active) is often used to enhance the stability of avobenzone (Source: Photochemistry and Photobiology, September 2001, pages 401–406). It is also important to note that all sunscreen ingredients break down to some extent when exposed to sunlight, which is why reapplication of sunscreen is critical to maintaining protection.

Interestingly, the press releases touting Mexoryl SX’s superiority as a UVA-protecting sunscreen ingredient don’t mention the active ingredients titanium dioxide and zinc oxide, which have long been available worldwide in sunscreen formulations, and that offer protection across a greater range of wavelengths with almost no possible risk of irritation, which is a pervasive problem with synthetic sunscreen agents such as Mexoryl SX. Regarding protection, UVA rays have a range of 320–400 nanometers. Although Mexoryl SX protects within this range, titanium dioxide and zinc oxide protect across the entire UVA and UVB spectrum, from 230 to 700 nanometers. Mexoryl SX is an effective UVA sunscreen agent, but it is by no means the only or absolute best one to look for.

mica. Earth mineral included in products to give them sparkle and shine.

microcrystalline wax. Plastic-type, highly refined wax derived from petroleum. Used as a thickener and to give products a semi-solid to solid smooth texture.

Microcystis aeruginosa. Latin name for spirulina. See algae.

milk protein. See protein.

milk vetch root. There is a good deal of research showing this root has antioxidant properties (Source: http://www.naturaldatabase.com), but there is little evidence that it functions that way when applied topically.

millet seed extract. Extract from a cereal grain that has no established benefit for skin, but is added to cosmetic formularies as a skin-conditioning agent.

mimosa oil or extract. Extract used as a fragrance in cosmetics.

mineral oil. Clear, odorless oil derived from petroleum that is widely used in cosmetics because it rarely causes allergic reactions and it cannot become a solid and clog pores. Despite mineral oil’s association with petroleum and the hype that it is bad for skin, keep in mind that petroleum is a natural ingredient derived from the earth and that once it becomes mineral oil USP (cosmetics- and pharmaceutical-grade mineral oil), it has no resemblance to the original petroleum. Cosmetics-grade mineral oil and petrolatum are considered the safest, most nonirritating moisturizing ingredients ever found (Sources: Cosmetics & Toiletries, January 2001, page 79; and Cosmetic Dermatology, September 2000, pages 44–46). Yes, they can keep air off the skin to some extent, but that’s what a good antioxidant is supposed to do; they don’t suffocate skin! Moreover, mineral oil and petrolatum are known to be efficacious in wound healing, and are also among the most effective moisturizing ingredients available (Source: Cosmetics & Toiletries, February 1998, pages 33–40).

mint. Can be a skin irritant and cause contact dermatitis. See counter-irritant.

Mitracarpe scaber extract. Extract from a plant native to West Africa, it has been shown to have some antimicrobial properties (Source: Letters in Applied Microbiology, February 2000, pages 105–108).

mixed fruit extracts. See sugarcane extract.

montmorillonite. See bentonite.

Morus bombycis root extract. See mulberry extract.

Morus nigra root extract. See black mulberry.

mucopolysaccharide. Also known as glycosaminoglycans. This is a large class of ingredients that includes hyaluronic acid, which is found universally in skin tissue. These substances, in association with protein, bind water and other cellular elements so they remain intact, forming a matrix that holds skin cells together. See natural moisturizing factor (NMF) and intercellular matrix.

Mucor miehei extract. Extract of a type of mold whose enzymes are used as a food additive and flavor enhancer in cheeses. It has no established benefit for skin, though companies using this ingredient often describe its enzymatic action as being akin to exfoliation. If that is the case, there is no proof to support the claims.

mugwort extract. There is no research showing this extract has any benefit for skin (Sources: http://www.naturaldatabase.com; and http://www.pubmed.com).

mulberry extract. Due to its arbutin content, this extract can have some value in preventing melanin production. Although there is limited research showing this to be the case, the research has been done only in vitro (Sources: eMedicine Journal, November 5, 2001, volume 2, number 11, http://www.emedicine.com; and Biophysical Research Communications, volume 243, number 3, pages 801–803). See arbutin.

myristic acid. Detergent cleansing agent that also creates foam and can be drying. See surfactant.

myristyl myristate. Used in cosmetics as a thickening agent and emollient.

myrrh. Fragrant gum resin that can be a skin irritant. There is little research showing it has any benefit for skin (Source: Healthnotes Review of Complementary and Integrative Medicine, http://www.healthwell.com/healthnotes/), although there is a small amount of research showing it may have antifungal and antibacterial properties (Source: Planta Medica, May 2000, pages 356–358).

myrtle extract. Contains volatile oil and tannins, and can have fungicidal, disinfectant, and antibacterial properties. It contains 1,8-cineole, a constituent responsible for toxicity. It is recommended that this not come in contact with skin (Sources: Journal of Natural Products, March 2002, pages 334–338; and http://www.naturaldatabase.com).

Myrtus communis extract. See myrtle extract.