Skin Care Cosmetics Ingredients Glossary

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Idebenone. A synthetic antioxidant similar to coenzyme Q10. Idebenone got a lot of press as the best antioxidant going when Allergan launched their Prevage product. The study that showed idebenone has the antioxidant muscle to surpass others involved only 30 subjects, and compared idebenone to vitamins C and E, alpha lipoic acid, coenzyme Q10, and kinetin. The study did not, however, compare the effects of idebenone to many of the hundreds of other potent antioxidants that commonly appear in other skin-care products, nor did it compare the effects of idebenone with the effects of a combination of antioxidants. Perhaps a cocktail of antioxidants would far surpass idebenone—we don’t know. Interestingly, a study comparing the protective effect of idebenone on sun-exposed skin found it ineffective compared to topical application of vitamins C and E with ferulic acid, but this study was conducted in part by Dr. Sheldon Pinnell, whose Skinceuticals line sells an antioxidant serum with those very ingredients. Other published studies compared the red grape antioxidant compound reseveratrol and L-ergothioneine to idebenone and found both superior to idebenone.

The world of antioxidants is far more complex than the mere handful that Allergan compared to idebenone. To date, there are still no published, peer-reviewed studies that support idebenone’s alleged superiority. This does not mean idebenone is not a valid antioxidant for skin. Given what we know about how ubiquinone performs in the body, it is definitely not a throwaway ingredient. What is fairly certain, however, is that it is neither the best nor most potent antioxidant around.

Ilex paraguariensis. See yerba mate extract.

Illicium vernum. See anise.

imidazolidinyl urea. Formaldehyde-releasing preservative. See formaldehyde-releasing preservative.

inactive ingredient. The list of inactive ingredients is the part of an ingredient label that is not regulated by the FDA other than the requirement that it be a complete list of the contents in descending order of concentration; that is, the ingredient with the largest concentration is listed first, then the next largest, and so forth. Thousands and thousands of inactive ingredients are used in cosmetics, and there is controversy about how truly inactive these substances are in regard to safety as well as about their long-term or short-term effects on skin or the human body.

inositol. Major component of lecithin that may have water-binding properties for skin. It is not a vitamin, although it is sometimes mistakenly thought of as a B vitamin.

insulinlike growth factor (IGF). Stimulates fat cells and connective tissue cells. See human growth factor.

intercellular matrix. “Mortar” that holds layers of skin cells together, creating a contiguous natural, external barrier. Preserving the intercellular layer intact keeps bacteria out, moisture in, and the skin’s surface smooth. Skin’s intercellular matrix  includes ceramides, hyaluronic acid, vitamin C, glycerin, cholesterol, and free fatty acids. See natural moisturizing factor (NMF).

interleukin (IL). Stimulates growth of white blood cells. See human growth factor.

Inula helenium. See elecampane.

iodopropynyl butylcarbamate. Used as a preservative in cosmetics. See preservatives.

Iris florentina extract. See orris root.

Irish moss extract. Type of red algae. See algae.

iron oxides. Compounds of iron that are used as colorings in some cosmetics. They also are used as a metal polish called jewelers’ rouge, and are well-known in their crude form as rust.

isobutyl acetate. See solvent.

isobutylparaben. See parabens.

isocetyl salicylate. See sodium salicylate.

isododecane. Hydrocarbon ingredient used as a solvent. Isododecane enhances the spreadability of products and has a weightless feel on skin. All hydrocarbons used in cosmetics help prevent the evaporation of water from the skin.

isoflavone. Plant estrogen with potent antioxidant properties (Source: Free Radical Biology and Medicine, December 2001, pages 1570–1581).

isohexadecane. Used as a detergent cleansing agent, emulsifier, and thickening agent in cosmetics.

isoleucine. See amino acid.

isoparaffin. See paraffin.

isopropyl alcohol. See alcohol.

isopropyl lanolate. Derived from lanolin, it is used in cosmetics as a thickening agent and emollient.

isopropyl myristate. Used in cosmetics as a thickening agent and emollient. Historically, animal testing has shown it causes clogged pores. Results derived from animal testing were eventually considered unreliable, however, and there is no subsequent research showing this ingredient is any more of a problem for skin than other emollient, waxy, thickening ingredients used in cosmetics.

isopropyl palmitate. Used in cosmetics as a thickening agent and emollient. As is true for any emollient or thickening agents, it can potentially clog pores, depending on the amount in the product and your skin’s response.

isostearamide DEA. Used as a surfactant, water-binding agent, and thickening agent. See surfactant, water-binding agent, and thickening agent.

isostearic acid. Fatty acid used as a binding agent and thickener. See fatty acid.

isotretinoin. See Accutane.

ivy extract. See English ivy extract.