S–Z

The science behind the ingredients in skincare.

S

Salicylic Acid

Type: Beta hydroxy acid (BHA) / aromatic hydroxy acid

A lipid-soluble organic acid widely used in cosmetic and dermatological formulations.

In skincare: Helps exfoliate the stratum corneum and is particularly useful in formulations for blemish-prone skin, clogged pores, and uneven texture.

Skin biology: Its lipophilic character allows it to interact effectively with the lipid-rich environment of the follicular opening.

Formulation note: Concentration, pH, vehicle, and regulatory classification determine how the ingredient may be used.

Squalane

Type: Saturated hydrocarbon / emollient

A hydrogenated, highly stable derivative of squalene.

In skincare: Functions primarily as a lightweight emollient and skin-conditioning ingredient.

Skin biology: Squalene is naturally present in human sebum; squalane is the more oxidation-resistant cosmetic form.

Formulation benefit: Provides excellent slip and softness without the oxidative instability associated with unsaturated squalene.

Squalene

Type: Unsaturated hydrocarbon / sebaceous lipid

A naturally occurring lipid found in human sebum and various plant and animal sources.

In skin: Contributes to the lipid composition of the skin surface.

In skincare: Used as an emollient, although its susceptibility to oxidation has led to widespread replacement by the more stable squalane.

Sodium Hyaluronate

Type: Salt form of hyaluronic acid / glycosaminoglycan

The sodium salt of hyaluronic acid.

In skincare: Functions primarily as a humectant and skin-conditioning agent.

Skin biology: Hyaluronan is naturally abundant in the extracellular matrix and contributes to tissue hydration and mechanical properties.

Formulation note: Molecular weight, concentration, and formulation environment influence its behavior.

Sodium PCA

Also known as: Sodium pyrrolidone carboxylate
Type: Humectant / natural moisturizing factor component

The sodium salt of pyroglutamic acid.

In skin: Naturally associated with the natural moisturizing factor (NMF) of the stratum corneum.

In skincare: Highly effective as a humectant and skin-conditioning ingredient.

Sodium Lactate

Type: Humectant / lactate salt

The sodium salt of lactic acid.

In skincare: Functions primarily as a humectant and pH-buffering ingredient.

Skin biology: Lactate is naturally present in the skin and contributes to the water-binding environment of the stratum corneum.

Shea Butter

INCI: Butyrospermum Parkii Butter
Type: Botanical butter / lipid mixture

A semi-solid lipid obtained from the nuts of the shea tree.

In skincare: Provides emollience, occlusive conditioning, and texture.

Composition: Rich in stearic and oleic acids, with an unsaponifiable fraction containing additional bioactive compounds.

Formulation use: Common in creams, balms, body butters, and barrier-oriented formulations.

Stearic Acid

Type: Saturated fatty acid

A long-chain fatty acid found naturally in skin lipids and many plant and animal fats.

In skincare: Functions as an emollient, thickener, consistency agent, and formulation lipid.

Formulation note: Often used in creams and emulsions alongside other fatty acids and emulsifiers.

Stearyl Alcohol

Type: Long-chain fatty alcohol

A saturated fatty alcohol derived from stearic acid.

In skincare: Functions as an emollient, thickener, stabilizer, and consistency agent.

Important distinction: Stearyl alcohol is a fatty alcohol and is not equivalent to ethanol or other volatile alcohols.

Succinic Acid

Type: Dicarboxylic acid

An organic acid that occurs naturally as an intermediate in cellular metabolism.

In skincare: Used primarily as a pH-adjusting and formulation ingredient and is also investigated in blemish-focused cosmetic systems.

Sunflower Seed Oil

INCI: Helianthus Annuus Seed Oil
Type: Botanical oil

A vegetable oil derived from sunflower seeds.

In skincare: Functions as an emollient and skin-conditioning lipid.

Composition: Depending on cultivar, sunflower oil may contain substantial amounts of linoleic or oleic acid.

Skin biology: High-linoleic sunflower oil is particularly relevant to formulations designed around epidermal barrier lipids.

T

Tocopherol

Common name: Vitamin E
Type: Lipid-soluble antioxidant

A naturally occurring form of vitamin E.

In skincare: Functions primarily as an antioxidant and skin-conditioning ingredient.

Formulation science: Tocopherol can help protect lipid components of formulations from oxidation, although its effectiveness depends on concentration and formulation environment.

Tocopheryl Acetate

Also known as: Vitamin E acetate
Type: Vitamin E ester

An esterified form of tocopherol designed for improved formulation stability.

In skincare: Used as a skin-conditioning ingredient and vitamin E derivative.

Important distinction: Tocopheryl acetate must be distinguished chemically and biologically from free tocopherol.

Tranexamic Acid

Type: Synthetic lysine analogue / antifibrinolytic compound

A synthetic derivative of the amino acid lysine.

In skincare: Used in formulations targeting the appearance of uneven pigmentation and discoloration.

Skin biology: Its cosmetic use is associated with modulation of pathways involved in pigment-related signaling.

Formulation note: Cosmetic concentrations and regulatory status vary by jurisdiction.

Trehalose

Type: Disaccharide / humectant

A naturally occurring sugar composed of two glucose units.

In skincare: Functions as a humectant and skin-conditioning ingredient.

Biological relevance: Trehalose is particularly interesting because certain organisms use it as a protective osmolyte under environmental stress.

Triethanolamine

Type: Amino alcohol / pH adjuster

A multifunctional alkaline compound used in cosmetic formulation.

In skincare: Primarily functions as a pH adjuster and emulsification aid.

Formulation note: It can neutralize acidic ingredients such as fatty acids to create soaps or contribute to emulsion structure.

Triglycerides

Also known as: Triacylglycerols
Type: Lipids

Molecules consisting of glycerol esterified with three fatty acids.

In skincare: Major components of many plant oils, animal fats, and cosmetic emollients.

Skin biology: Triglycerides contribute to the lipid environment of the skin surface and can influence moisturization and sensory properties.

Turmeric Extract

INCI: Curcuma Longa Root Extract
Type: Botanical extract

An extract obtained from turmeric rhizomes.

In skincare: Used primarily for antioxidant and skin-conditioning purposes.

Key constituents: Curcuminoids are among the best-known compounds associated with turmeric.

Formulation note: Curcuminoids have limited water solubility and can strongly influence formulation color.

U

Ubiquinone

Also known as: Coenzyme Q10 / CoQ10
Type: Quinone antioxidant

A lipid-soluble molecule involved in mitochondrial electron transport.

In skincare: Used primarily for antioxidant and skin-conditioning applications.

Skin biology: Coenzyme Q10 participates in cellular energy metabolism and antioxidant defense.

Urea

Type: Humectant / keratolytic / natural moisturizing factor component

A small nitrogen-containing molecule naturally present in the skin's natural moisturizing factor.

In skincare: At lower concentrations, functions primarily as a humectant; at higher concentrations, it can contribute to softening and keratolytic activity.

Skin biology: Urea is an important component of normal stratum-corneum hydration.

Undecylenic Acid

Type: Unsaturated fatty acid

A fatty acid derived from ricinoleic acid through industrial processing.

In skincare: Used in certain formulations for skin conditioning and antimicrobial-support applications.

V

Vitamin C

Also known as: Ascorbic acid and vitamin C derivatives
Type: Antioxidant vitamin

A collective term encompassing ascorbic acid and several chemically modified vitamin C derivatives used in cosmetics.

In skincare: Associated with antioxidant defense, collagen-related biological processes, and the appearance of uneven pigmentation.

Important distinction: Vitamin C derivatives differ substantially in chemistry, stability, penetration, conversion, and evidence.

Vitamin E

Also known as: Tocopherols and tocotrienols
Type: Lipid-soluble antioxidant

A family of related compounds rather than a single molecule.

In skincare: Used primarily for antioxidant protection and skin conditioning.

Formulation science: Vitamin E is particularly relevant to protecting lipid-rich systems against oxidative damage.

Vaccinium Myrtillus Fruit Extract

Common name: Bilberry extract
Type: Botanical extract

An extract derived from bilberry fruit.

In skincare: Used primarily for antioxidant and skin-conditioning applications.

Composition: Contains anthocyanins and other polyphenolic compounds.

Vitis Vinifera Seed Extract

Common name: Grape seed extract
Type: Botanical extract

An extract obtained from grape seeds.

In skincare: Used primarily for antioxidant and skin-conditioning purposes.

Key constituents: Often contains oligomeric proanthocyanidins and other polyphenols, although composition varies with extraction.

W

Water

Also known as: Aqua
Type: Solvent

The most common cosmetic solvent and a fundamental component of many skincare formulations.

In skincare: Dissolves or disperses numerous water-soluble ingredients and provides the continuous phase of many emulsions, gels, and serums.

Formulation science: Water quality is critical. Purified water is generally required to control microbial contamination, dissolved minerals, and other impurities.

Witch Hazel

INCI: Hamamelis Virginiana Extract / Distillate
Type: Botanical preparation

Derived from Hamamelis virginiana.

In skincare: Traditionally used for astringent, cleansing, and skin-conditioning purposes.

Important distinction: Witch-hazel products can differ substantially depending on whether they are extracts, distillates, or alcohol-containing preparations.

X

Xanthan Gum

Type: Microbial polysaccharide / rheology modifier

A polysaccharide produced through microbial fermentation.

In skincare: Functions primarily as a thickener, stabilizer, suspending agent, and rheology modifier.

Formulation benefit: Helps control viscosity and keeps dispersed ingredients from settling.

Important distinction: Xanthan gum generally changes the physical structure and flow behavior of a formulation rather than acting as a conventional skincare active.

Xylitol

Type: Sugar alcohol / humectant

A five-carbon sugar alcohol naturally found in various fruits and plant materials.

In skincare: Functions as a humectant and skin-conditioning ingredient.

Formulation science: Its water-binding characteristics make it useful in moisturizing systems.

Y

Yeast Extract

Type: Fermentation-derived biological extract

A complex mixture obtained from yeast biomass or fermentation processes.

In skincare: Used for skin conditioning, hydration, and formulation-specific biological activity, depending on the extract.

Composition: May contain peptides, amino acids, carbohydrates, minerals, nucleotides, and other yeast-derived constituents.

Important distinction: "Yeast extract" does not represent one chemically standardized molecule; composition depends heavily on the production process.

Yucca Root Extract

INCI: Yucca Schidigera Root Extract
Type: Botanical extract

An extract obtained from the roots of Yucca schidigera.

In skincare: Used primarily as a skin-conditioning and formulation-support ingredient.

Composition: May contain steroidal saponins and other plant constituents.

Z

Zinc Oxide

Type: Mineral / inorganic UV filter

An inorganic compound composed of zinc and oxygen.

In skincare: Used as a UV filter, skin protectant, and opacifying ingredient.

Skin biology: Zinc oxide particles interact with and attenuate ultraviolet radiation through absorption and scattering.

Formulation note: Particle size, surface treatment, dispersion quality, and coating can substantially influence cosmetic performance.

Zinc PCA

Type: Zinc salt / skin-conditioning ingredient

A zinc salt associated with pyrrolidone carboxylic acid.

In skincare: Used in formulations targeting oiliness, skin conditioning, and hydration.

Formulation science: Combines the properties associated with zinc ions and PCA in a single ingredient.

Zinc Sulfate

Type: Inorganic zinc salt

A water-soluble zinc compound.

In skincare: Used in selected cosmetic formulations as a skin-conditioning and formulation ingredient.

Formulation note: Concentration and compatibility are important because inorganic salts can influence pH, ionic strength, and formulation stability.

Zingiber Officinale Root Extract

Common name: Ginger root extract
Type: Botanical extract

An extract derived from ginger rhizomes.

In skincare: Used primarily for antioxidant and skin-conditioning applications.

Composition: Contains gingerols, shogaols, and other phytochemicals whose concentrations vary according to extraction and processing.

Ziziphus Jujuba Fruit Extract

Common name: Jujube extract
Type: Botanical extract

An extract obtained from the fruit of Ziziphus jujuba.

In skincare: Used primarily as a skin-conditioning and botanical antioxidant ingredient.