Ranunculus ficaria extract. Extract that may have antibacterial and antifungal properties and that is used in the treatment of hemorrhoids. However, applied topically it can cause skin irritation and may also cause photodermatitis (Source: http://www.naturaldatabase.com).

rapeseed oil. Nonfragrant oil that has emollient and potential antioxidant properties for skin (Source: British Journal of Nutrition, May 2002, pages 489–499).

raspberry seed extract. See red raspberry extract.

raspberry seed oil. See red raspberry extract.

red algae. See algae.

red clover. Can have antioxidant and anti-inflammatory properties (Source: Photochemistry and Photobiology, September 2001, pages 465–470). It is sold as an herbal supplement for relief of menopausal symptoms such as hot flashes and vaginal dryness. Red clover does contain high concentrations of four major isoflavones that have been shown to have estrogenic properties. However, in studies, red clover was found to be no better than a placebo for menopausal symptoms (Sources: Harvard Women’s Health Watch, December 2001, http://www.health.harvard.edu/medline/Women/W1201e.html; and http://www.naturaldatabase.com).

red raspberry extract. Fruit extract that has potent antioxidant properties (Source: Journal of Agricultural Food Chemistry, June 5, 2002, pages 3495–3500) and antibacterial properties (Source: International Journal of Food Microbiology, May 2000, pages 3–12). It also can cause irritation due to its tannin content.

red sandalwood. Has a phytoestrogen component (Source: Phytochemistry, March 2000, pages 605–606), but can also be a skin irritant (Source: Contact Dermatitis, January 1996, page 69).

reducing agent. In cosmetics, substance that has the ability to split or break down the disulfide bonds of hair. Therefore, reducing agents are typically used in hair-straightening or hair-waving products and in depilatories. The chemical reaction they generate has antioxidant properties, but they can also be strong skin irritants.

Renova. See Retin-A and tretinoin.

resorcinol. Considered an effective topical disinfectant in concentrations of 1% to 3% (Source: http://www.fda.gov). However, there is also research showing it to be overly irritating for skin (Source: Journal of the European Academy of Dermatology and Venereology, July 1999, pages 14–23). As a result it is rarely used nowadays for treating blemishes.

resveratrol. Potent polyphenolic antioxidant that is abundant in red grapes and, therefore, in red wine (unfortunately for some of us, not in white wine). Resveratrol has been reported in numerous studies to be one of the most potent natural chemopreventive agents inhibiting the cellular processes associated with tumor development, including initiation, promotion, and progression. It also has significant anti-inflammatory properties. Conversely, there is research showing it to be associated with cell death when applied topically if skin is exposed to sunlight (Sources: Anticancer Research, September–October 2004, pages 2783–2840; Medicinal Chemistry, November 2005, pages 629–633; Molecular Nutrition and Food Research, May 2005, pages 405–430; Antioxidant Redox Signal, December 2001, pages 1041–1064; and Mutation Research, Genetic Toxicology and Environmental Mutagenesis, September 2001, pages 171–180).

Retin-A. One of several prescription-only drugs (others include Renova, Retin-A Micro, and Avita) that contain tretinoin (technical name: all-trans retinoic acid), which is the acid form of vitamin A, as the active ingredient. In skin, tretinoin is the form of vitamin A that can actually affect cell production by binding to the tretinoin receptor sites on the cell. There is a great deal of research establishing that tretinoin is effective in improving cell production in skin that has been damaged (often by exposure to sunlight). Tretinoin is a valid method for addressing wrinkles and, overall, for improving cell production. Applying tretinoin does not produce miraculous results, but the positive outcome in terms of skin health is indisputable. However, it is highly possible that applying tretinoin to the skin will cause irritation, which is a major drawback of this drug. See tretinoin.

retinol. If the layers of connective tissue beneath the skin on the thighs are indeed the main cause of cellulite (along with excess or poorly formed fat deposits), then improving skin structure should, theoretically, make a difference, and there is growing evidence that this is the case. Retinol (the entire vitamin A molecule) is one of the ingredients known to help improve skin structure. Of all the ingredients to look for in a cellulite product, this should be at the top of the list. However, most cellulite products contain only teeny amounts of retinol (at best) and are often in packaging that won’t keep this air-sensitive ingredient stable. One other point: Johnson & Johnson has a study showing that a combination of retinol, caffeine, and ruscogenine can reduce the appearance of cellulite. Of course, J&J-owned companies RoC and Neutrogena both sell cellulite products with that combination of ingredients (Sources: Journal of Cosmetic Science, July–August 2001, pages 199–210; Journal of the European Academy of Dermatology & Venereology, July 2000, page 251; and American Journal of Clinical Dermatology, November–December 2000, pages 369–374).

retinyl palmitate. Form of vitamin A. It is a combination of retinol (pure vitamin A) and palmitic acid. There is research showing it to be effective as an antioxidant and skin-cell regulator (Sources: European Journal of Medical Research, September 2001, pages 391–398; and Journal of Investigative Dermatology, September 1997, pages 301–305). See retinol.

riboflavin. See vitamin B2.

rice bran oil. Emollient oil similar to other nonfragrant plant oils. There is no research showing this has any superior benefit for skin.

rice oil. Emollient similar to other nonfragrant plant oils. There is no research showing this has any superior benefit for skin.

rice starch. Absorbent substance sometimes included in products rather than talc. It can cause allergic reactions and, because it is a food derivative (as opposed to a mineral derivative like talc), it can support bacterial growth in pores.

ricinoleate. Glyceryl triester used in cosmetics as a thickening agent and emollient.

Ricinus communis. See castor oil.

RNA. Ribonucleic acid is a single strand of molecules, copied exactly from the DNA in the cell nucleus, that is required for the body’s production of protein. This single strand is a linear, ladder-like sequence of nucleotide bases (chemicals that form its structure) that corresponds precisely to the sequence of bases in the DNA strand (the core of the body’s genetic makeup). RNA in a skin-care product is useless because it cannot affect a cell’s genetic elements. The production of DNA and RNA is an extremely complex process that requires a multitude of proteins and enzymes to have its effect on the body’s genetic material. And let me say that it is doubtful that you would ever want to put anything on your skin that could affect your genetic material, and particularly not via a cosmetic, for which there are no safety or efficacy regulations.

Robinia pseudacacia extract. See black locust extract.

Rosa canina. See rose hip oil.

Rosa centifolia. See rose hip oil.

Rosa centifolia flower. See rose hip.

Rosa damascena oil. Oil of a very fragrant pink rose used as fragrance in cosmetics.

Rosa eglanteria. See rose hip oil.

Rosa gallica flower extract. Fragrant extract.

Rosa mosqueta. See rose hip oil.

Rosa roxburghii extract. Extract from the chestnut rose; can be a source of antioxidants for skin, and does not impart fragrance (Source: International Journal of Clinical Chemistry and Applied Molecular Biology, November 2001, pages 37–43).

Rosa rubiginosa. See rose hip oil.

rose flower. Highly fragrant substance that can be a skin irritant.

rose flower oil. Fragrant, volatile oil that can be a skin irritant and sensitizer. There is no research showing this has any benefit for skin.

rose hip. Seed-containing part of a rose. See rose hip oil and vitamin C.

rose hip oil. Good emollient oil that has antioxidant properties (Sources: Journal of Agricultural Food Chemistry, March 2000, pages 825–828; and Journal of Nutrition, March 2002, pages 461–471).

rose oil. Fragrant, volatile oil that can be a skin irritant and sensitizer.

rosemary extract. Extract that can have antioxidant benefit for skin (Source: Journal of Agricultural Food Chemistry, October 1999, pages 3954–3962), but its aromatic components can cause irritation or sensitizing or toxic reactions on skin (Source: Chemical Research in Toxicology, November 2001, pages 1546–1551).

rosemary oil. See rosemary extract.

Rosmarinus officinalis extract. See rosemary extract.

royal jelly. Milky white, thick substance secreted by worker bees that has been shown to have some immune-modulating benefits (Source: Comparative Immunology, Microbiology and Infectious Diseases, January 1996, pages 31–38). The myriad other claims about royal jelly, such as being able to prevent wrinkles and heal acne, are all anecdotal and have no research to substantiate them.

Rubus idaeus. See red raspberry extract.

Rubus occidentalis. See black raspberry.

Rubus ursinus. See marionberry.

Rubus ursinus x idaeus. See boysenberry.

Ruscus aculeatus. See butcher’s broom extract.

rutin. Bioflavonoid that is extracted from various plants and used in cosmetics as an antioxidant and emollient (Sources: Cell Biology and Toxicology, 2000, volume 16, number 2, pages 91–98; and Life Sciences, January 14, 2000, pages 709–723). See bioflavonoid.