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Rating Ingredient
Best

idebenone

A synthetic antioxidant similar to coenzyme Q10. Idebenone got a lot of press as the best...

Categories: Antioxidants
Best

Ilex paraguariensis

Poor

Illicium vernum

Average

imidazolidinyl urea

Considered a weaker preservative than its "cousin" diazolidinyl urea because it is beneficial against...

Categories: Preservatives
Good

inactive ingredient

The list of inactive ingredients is the part of an ingredient label that is not regulated by the...

Categories: Miscellaneous
Best

inositol

Major component of lecithin that may have water-binding properties for skin. It is not a vitamin,...

Categories: Skin-Replenishing
Poor

Inula helenium

Good

iodopropynyl butylcarbamate

A synthetic preservative that is typically used in concentrations of 0.1% or less. It is very...

Categories: Preservatives
Poor

Iris florentina extract

Good

Irish moss extract

Type of red algae.

Good

iron oxides

Compounds of iron that are used as colorings in some cosmetics. They also are used as a metal...

Average

iron powder

Iron powder is, as the name states, a powdered versoin of the mineral iron. A natural ingredient, it's used as an opacifying agent in cosmetics.

Categories: Absorbent
Good

isoamyl laurate

The ester of isoamyl alcohol and lauric acid, this plant- or synthetic-based texture-enhancing ingredient feels velvety-soft.

Good

isobutyl acetate

Categories: Miscellaneous
Good

isobutylparaben

Parabens are a group of controversial preservatives that include butylparaben...

Categories: Preservatives
Average

isocetyl salicylate

Categories: Miscellaneous
Good

isododecane

Hydrocarbon ingredient used as a solvent. Isododecane enhances the spreadability of products and...

Best

isoflavone

Plant derivative with antioxidant properties...

Good

isohexadecane

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

Good

isoleucine

Good

isononyl isononanoate

An ester that functions as a skin-conditioning agent. Occurs naturally in cocoa and lavender oil.

Categories: Emollients
Good

isoparaffin

Poor

isopropyl alcohol

Categories: Sensitizing
Good

isopropyl isostearate

The ester of isopropyl alcohol and isostearic acid. It is used as a skin-conditioning agent and emollient in cosmetics products...

Categories: Emollients
Good

isopropyl lanolate

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

Good

isopropyl myristate

Texture enhancer and emollient as used in cosmetics.

Good

isopropyl palmitate

Texture enhancer and emollient as used in cosmetics. It can potentially be...

Good

isopropyl titanium triisostearate

A synthetic or animal-derived ingredient used as a surface treatment for cosmetic pigments...

Good

isopropyl titanium triisostearte/triethoxycaprylylsilane crosspolymer

A synthetic, silicone-enhanced polymer that occurs from combining isopropyl titanium triisostearate...

Good

isostearamide DEA

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

Good

isostearic acid

Fatty acid used as a binding agent and thickener.

Poor

ivy extract

Plant extract that can be sensitizing due to its astringent (skin-constricting) properties.

About the Experts

Paula Begoun is the best-selling author of 20 books about skincare and makeup. She is known worldwide as The Cosmetics Cop and creator of Paula’s Choice Skincare. Paula’s expertise has led to hundreds of appearances on national and international radio, print, and television including:

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The Paula's Choice Research Team is dedicated to busting beauty myths and providing expert advice that solves your skincare frustrations so you can have the best skin of your life!