I

indigo dye

See colors.

colors.

indole

This crystalline compound, found in jasmine oil and civet, is a product of the decomposition of proteins containing the amino acid tryptophan. Although indole has an unpleasant odor, it’s used as a trace ingredient in perfumes.

ingest

To take into the body by mouth.

inflammation

A reaction of the body to irritation, marked by redness, itching, swelling, heat and pain. Skin problems of this type can be allergic reactions to topical cosmetics.

ing,’own hair

A hair that grows underneath the skin. Ingrown hairs can cause infections.

ingrown nail

The growth of the nail inward towards the skin instead of outward towards the finger or toe. It can cause pain and possibly an infection.

inorganic

Matter not related to, and lacking the structure of, living organisms. In chemistry, inorganic pertains to compounds that don’t contain hydrocarbons but do contain oxides and sulfides of carbon. Compare organic.

organic.

inositol

This B vitamin, usually associated with choline, occurs naturally in lecithin (which the body produces). As part of lecithin, inositol helps metabolize fats and dissolves cholesterol. Although more inositol is found in the body than any other nutrient except niacin, no minimum daily requirement for this substance in human nutrition has been established. Also see vitamin B complex.

vitamin B complex.

insoluble

Incapable of dissolving or very difficult to dissolve. Also, in reference to collagen, incapable of absorbing moisture.

in vitro

This term refers to experiments carried out in an artificial environment, outside of living organisms. (Literally, it means "in glass"—in other words, in a test tube, laboratory flask or similar type of equipment.) Compare in vivo.

in vivo

Within a living organism, as opposed to in vitro.

iodine

This nonmetallic element occurs in seawater and in plants and animals that grow in the sea. Iodine is necessarv for correct functioning of the thyroid gland; when applied topically’, it has antiseptic benefits.

Ion

An atom or a group of atoms that carries an electrical charge. Positive ions are called cations and negative ions are called anions.

ionization

By utilizing an electric current, an aesthetician can force positive ions through a moisturizing cream or lotion to assure deep penetration into the skin during a facial treatment.

Irgasan DP 300

This chemical, which is used in shampoos, soaps and deodorants, is phototoxic, environmentally toxic (because hydrocarbons pollute the air, water and land), and may be carcinogenic (because it’s a coal tar derivative). Another name for this diphenyl ether compound (also known as a biphenyl) is triclosan.

iron oxides

Also known as jewelers’ rouge, or simply as rust, these compounds are used as colorings in some cosmetics. Also see colors and hematite.

isopropyl alcohol

This synthetic fatty alcohol, made from propylene and sulfuric acid, is used as an antiseptic, a solvent, a rubbing alcohol and as a source for acetone. Also see alcohol.

isopropyl lanolate, laurate, linoleate, oleate, palmitate, stearate and isostearate

These esters of isopropyl alcohol and various fatty acids are synthetic chemicals that can irritate and cause aller~jc reactions.

isopropyl myristate

This synthetic chemical is used as an emollient and a lubricant, and to reduce the greasy feel caused by the high oil content of other ingredients. It can cause allergic reactions and should be avoided. See fatty alcohols.