oak root extract. Extract that may have antibacterial properties on skin, but that also can be a skin irritant.

oatmeal. Can have anti-irritant and anti-inflammatory properties (Source: Skin Pharmacology and Applied Skin Physiology, March–April 2002, pages 120–124).

octinoxate. See octyl methoxycinnamate.

octisalate. Technical name for the active sunscreen ingredient octyl salicylate (also known as ethylhexyl salicylate). See octyl salicylate.

octocrylene. Sunscreen agent that protects skin from the UVB range of sunlight (Sources: http://www.photodermatology.com/sunprotection.htm ; and Skin Therapy Letter, 1997, volume 2, number 5, http://www.dermatology.org/skintherapy ).

octyl methoxycinnamate. Sunscreen agent used to protect skin primarily from the sun’s UVB rays (Sources: http://www.photodermatology.com/sunprotection.htm; and Skin Therapy Letter, 1997, volume 2, number 5, http://www.dermatology.org/skintherapy ).

octyl palmitate. Used in cosmetics as a thickening agent and emollient.

octyl salicylate. Sunscreen agent used to protect skin primarily from the sun’s UVB rays (Sources: http://www.photodermatology.com/sunprotection.htm; and Skin Therapy Letter, 1997, volume 2, number 5, volume 2, number 5, http://www.dermatology.org/skintherapy).

octyl stearate. Used in cosmetics as a thickening agent and emollient.

octyldodecanol. Emulsifier and opacifying agent, used primarily as a thickener in moisturizers because of its lubricating and emollient properties.

octyldodecyl myristate. Mixture of octyldodecanol (thickener) and myristic acid that forms a new compound used as a skin-conditioning agent and emollient. See myristic acid.

octyldodecyl neopentanoate. Skin-conditioning agent and emollient.

o-cymen-5-ol. Preservative used in cosmetics. See preservatives.

Oenothera biennis oil. See evening primrose oil.

oleic acid. Fatty acid used as a surfactant and thickening agent. See fatty acid, surfactant, and thickening agent.

oleths. Mild surfactants. See surfactant.

oleyl erucate. Skin-conditioning agent derived from oleyl alcohol, which is obtained chiefly from fish oil.

olibanum extract. See frankincense extract.

olive oil. Emollient plant oil similar to all nonfragrant plant oils. The concept of olive oil having anti-aging properties stems from some evidence that diets high in olive oil may help prevent heart disease (Sources: European Journal of Clinical Nutrition, January 2002, pages 72–81; and Lipids, November 2001, pages 1195–1202, and Supplemental, pages S49–S52). There are also a small number of animal tests showing that topically applied olive oil can protect against UVB damage (Sources: Carcinogenesis, November 2000, pages 2085–2090; and Journal of Dermatological Science, March 2000, Supplemental, pages S45–S50). It does seem that olive oil is a good antioxidant and assuredly it’s a good moisturizing ingredient, but research shows similar results for other oils as well. See natural moisturizing factor (NMF).

opium poppy seed. Potent analgesic (Source: Phytotherapy Research, September 2000, pages 401–418), although there is no research showing this to be effective when applied topically to skin.

orange blossom. Fragrant extract that can also be a skin irritant.

Orbignya martiana. See babassu oil.

Orbignya oleifera. See babassu oil.

orchid. Fragrant flower that can be a skin irritant.

oregano. Has potent antibacterial and antifungal properties, but can also be a skin irritant (Source: Journal of Food Protection, July 2001, pages 1019–1024).

Origanum majorana. See marjoram.

Origanum vulgare flower extract. See oregano.

orris root. Used primarily as a fragrant component due to its violet-like scent (Source: http://www.botanical.com/botanical/mgmh/i/irises08.html). It can cause allergic or sensitizing skin reactions and there is no research showing it has any benefit for skin (Source: Botanical Dermatology Database, http://bodd.cf.ac.uk/BotDermFolder/BotDermC/CACT.html).

Ortho Tri-Cyclen. Low-dosage birth-control pills (generic norgestimate/ethinyl estradiol) approved for use in the United States for the treatment of acne. In Canada, the birth control pill Diane-35, a combination of cyproterone acetate and ethinyl estradiol, is approved for treatment of acne (Source: Skin Therapy Letter, 1999, volume 4, number 4, http://www.dermatology.org/skintherapy). According to a double-blind, placebo-controlled study published in Fertility and Sterility (September 2001, pages 461–468), other “low-dose birth-control pills can be an effective and safe treatment for moderate acne.” The double-blind, placebo-controlled, randomized clinical trial found that the birth-control pill containing levonorgestrel (Alesse) reduced the appearance of acne.

Oryza sativa oil. See rice oil.

oryzanol. Component of plants and their products, such as rice bran, that has potent antioxidant properties.

oxidoreductase. Large group of enzymes that reduce or block oxygen in different forms from generating free-radical damage.

oxybenzone. Sunscreen agent that protects primarily from the sun’s UVB rays, and some, but not all, UVA rays (Sources: http://www.photodermatology.com/sunprotection.htm; and Skin Therapy Letter, 1997, volume 2, number 5, http://www.dermatology.org/skintherapy). See UVA.

oxygen. Many cosmetic products contain antioxidants, ingredients that reduce the negative effect of oxygen or oxidative substances on skin. At the same time, the cosmetics industry also sells products that contain hydrogen peroxide (H2O2) or other oxygen-releasing ingredients, which supposedly deliver an oxygen molecule when they come in contact with skin, although that generates free-radical damage (Source: Human and Experimental Toxicology, February 2002, pages 61–62). Why the concern about supplying oxygen to the skin? Oxygen depletion is one of the things that happen to older skin, regardless of whether it’s been affected by sun damage or any other health-related factor. Why or how that happens is completely unknown, though it is thought to have something to do with blood flow and a reduction in lung capacity as we age. It is also believed that, with age, the issue isn’t so much the amount of oxygen but rather a change in the blood’s ability to use the oxygen it has.

However, when wound healing is a problem, regenerating the tissue often demands, in addition to other factors, increased topical oxygen, because wound repair can be facilitated by oxygen therapy. Yet this method of treating wounds lacks research showing it to be effective or to be the best option for skin (Source: Annals of the New York Academy of Sciences, May 2002, pages 239–249).

Oxidative stress is an unavoidable consequence of life in an oxygen-rich atmosphere. The “Oxygen Paradox” is that oxygen is dangerous to the very life forms for which it has become an essential component of energy production. The first defense against oxygen toxicity is the sharp reduction in the amount of oxygen present in cells, from the level present in air of 20% to a tissue concentration of only 3% to 4% oxygen. These relatively low tissue levels of oxygen mean that most oxidative damage never occurs. Cells, tissues, organs, and organisms have multiple layers of antioxidant defenses, plus damage replacement and repair systems to cope with the stress and damage that oxygen engenders (Source: Journal of the International Union of Biochemistry and Molecular Biology, October–November 2000, pages 279–289). See free-radical damage.

ozokerite. Mineral that is used as a thickening agent in cosmetics, especially in lipsticks and stick foundations.