Cosmetics Ingredient Dictionary

I

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 (Source: The Journal of Investigative Dermatology, May 2006, pages 1185–1187). Other published studies compared the red grape antioxidant compound reseveratrol and L-ergothioneine  to idebenone and found both superior to idebenone (Sources: Journal of Cosmetic Dermatology, March 2008, pages 2-7 and September 2007, pages 183-188).
 
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 (Source: Contact Dermatitis,
December 2000, pages 339–343). 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 (also referred to in this book as skin-identical ingredients) 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 (Source: Archives of Dermatology, June 1986, pages 660–665). 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. Anti-acne drug that’s derived from vitamin A. This drug works by essentially stopping oil production in sebaceous glands (the oil-producing structures of the skin) and literally shrinking these glands to the size of a baby’s (Source: Dermatology, 1997; volume 195, Supplemental 1:1–3, pages 38–40). This prevents sebum (oil) from clogging the hair follicle, mixing with dead skin cells, and rupturing the follicle wall to create an environment where the bacterium (Propionibacterium acnes) can thrive, which can result in pimples or cysts. Relatively normal oil production resumes when treatment is completed; although the sebaceous glands may slowly begin to enlarge again, they rarely become as large as they were before treatment. “Because of its relatively rapid onset of action and its high efficacy with reducing more than 90% of the most severe [acne] inflammatory lesions, isotretinoin [Accutane] has a role as an effective treatment in patients with severe acne that is recalcitrant to other therapies” (Source: Journal of the American Academy of Dermatology, November 2001, Supplemental, pages 188–194).

Isotretinoin is controversial, however, for several reasons, but principally because of its most insidious side effect—it has been proven to cause severe birth defects in nearly 90% of the babies born to women who were pregnant while taking it. Other commonly reported, although temporary, side effects of isotretinoin include dry skin and lips, mild nosebleeds (the inside of your nose can get really dry for the first few days), hair loss, aches and pains, itching, rash, fragile skin, increased sensitivity to the sun, headaches, and peeling palms and hands. More serious, although much less common, side effects include severe headaches, nausea, vomiting, blurred vision, changes in mood, depression, severe stomach pain, diarrhea, decreased night vision, bowel problems, persistent dryness of eyes, calcium deposits in tendons, an increase in cholesterol levels, and yellowing of the skin. However, there is current research indicating that depression does not occur during the course of taking isotretinoin (Sources: Canadian Journal of Clinical Pharmacology, June 2007, pages 277–233; Psychological Reports, December 2006, pages 897–906; European Journal of Dermatology, September–October, 2006, pages 565–571; and Journal of Drugs in Dermatology, May 2006, pages 467–468). See Accutane.

ivy extract. See English ivy extract.