Use this glossary to quickly look up professional skin care terms. Tap a letter in the table of contents to jump to that section.

---

A

Actinic Keratosis – A premalignant condition of thick, scaly, or crusty patches of skin. It is more common in fair-skinned people, especially those who are frequently exposed to the sun, as it is usually accompanied by solar damage. Since some of these pre-cancers progress to squamous cell carcinoma, they should be treated.

Alipidic – Skin that has an impaired barrier function including sebaceous secretions.

Aromatherapy – Ancient art of using scent to relieve physical symptoms (stress) or to accent feelings, i.e., peppermint invigorates. Plant derived essential oils are used in treatment and therapy to enhance the beauty of the skin and body.

Artery – Blood vessel which carries blood to the heart.

Arthrosis – Name under which are designated degenerative chronic conditions of the articulation of line or juncture between the bones. Causes pain, cracking, deformation or impotency without deterioration of general conditions.

Asphyxiated Skin – Impaired exchange of oxygen in the skin. Exchanges usually caused by excessive accumulation of keratin on skin surface, thus causing a dull, lifeless complexion. May be accompanied by numerous comedones and/or vesicles.

Asteatosis – Dry, scaly skin. Partial or absolute deficiency of lipids usually due to aging or bodily disorders. May be caused by alkalies found in soaps and washing powders.

Asthma – Term used to denote bronchial asthma; a condition of the lungs in which there is widespread narrowing of airways, varying over short periods of time either spontaneously or as a result of treatment, due in varying degrees to contraction (spasm) of smooth muscle, edema of the mucosa, and mucus in the lumen of the bronchi and bronchioles; these changes are caused by the local release of spasmogens and vaso-active substances in the course of an allergic process.

Astringent – Constricting action on the skin giving a tightening effect. Many botanicals provide an astringent effect due to the presence of tannins.

Atonic – Pertaining to the lack of tone such as seen in aging skin, and pre-mature aged skin due to photo damage.

B

Bacteria (Bacterium) – Microscopic unicellular plant lacking chlorophyll and fully defined nuclei. They occur in three main forms: spherical (coccus), rod-shaped (bacillus), and spiral (spirilla). They occur in water, soil, organic matter or living bodies of plants and animals, being saprophytic (absorbing), parasitic (living in or on one), and autotrophic in nutrition.

Barrier Vehicle – A substance that allows the flow of product into the skin (through the cell structure of the epidermis) or through keratinized structure such as a fingernail or hair.

Basal Lamina – Basement membrane.

Basal Layer – Innermost layer of the epidermis; contains living and dividing cells.

Base – In chemistry, a substance which when dissolved in water provides hydroxyl ions from its own molecules; a molecule or ion which can accept protons.

Basic Skin Care – Products that care for the needs of the skin on a day-to-day basis. Usually consists of a cleanser, freshener, and moisturizer.

Benign – Mild form of illness as opposed to fatal or malignant.

Binder – Substance such as gum Arabic, gum tragacanth, glycerin, and sorbitol that dispense, swell, absorb water, increase consistency, and hold ingredients together.

Bioextract – Extracts prepared from animal tissues. Soluble collagen and hydrolyzed elastin are two examples.

Blood Vessels – Network of tube-like vessels that supply nutrients and oxygen to the skin. Help regulate body temperature by contracting and expanding in response to external stimuli.

Botanical – Extract derived from plants. Botanicals are single compounds that are sometimes used in combination for a more powerful effect. Natural plant extracts are indigenous to many cultures and have been utilized as remedies for inner and outer health. Therapeutic benefits are emphasized in numerous medicinal remedies and beauty treatments.

Buffer – Usually a solution with a relatively constant acidity/alkalinity ratio used to lengthen the shelf life of the product and make it gentler on the complexion. A typical solution would be hydrochloric acid and sodium hydroxide.

C

CTFA – Cosmetic, Toiletries, Fragrances Association. An industry organization formed in order to self-regulate the industry rather than allow the FDA to step in and fill the regulatory vacuum with an abundance of forms and regulations.

Callous – Hard, tough area of skin created by friction.

Calor – Heat.

Carbuncle – Large circumscribed inflammation of the subcutaneous tissue similar to a furuncle, but more extensive.

Carrier – Referring to a substance that dispenses the active ingredient in a product. Effects product spreadability, stability and time release of active ingredients. A liposome is an example of a carrier.

Cartilage – Connective tissue characterized by lack of blood vessels and is of soft consistency.

Catabolism – Breakdown of complex compounds into simpler ones.

Catalyst – A substance that accelerates or initiates a chemical reaction but remains unchanged while performing this task many times. Words ending in “ase” such as “tyrosinase” are examples of enzymes that initiate melanin production.

Cell Membrane – Bi-layer of lipids and protein surrounding the cell.

Cellular Surface Cells or Debris – Refers to the natural sloughing off of the stratum corneum (outer epidermis) and is expelled by all living cells.

Centistoke – Measure of viscosity (thickness).

Chapping – Having or pertaining to skin that is dry, scaly, and fissured (cracked) due to cold exposure or excessive evaporation of moisture from the skin’s surface.

Chelating Agent – Substance that causes a metal ion to react with a molecule to form a chelate, a stable ring-like structure. Chelating agents include EDTA, Disodium EDTA, Trisodium EDTA, Tetrasodium EDTA and Disodium EDTA Copper. These compounds bind and precipitate metals such as Ethylenediamine Tetracetic Acid (EDTA), removing trace minerals.

Cheloids (Keloids) – Nodular, frequently lobulated, firm, moveable, non-encapsulated mass of hyperplastic scar tissue composed of irregular collagen bands. Occurs after trauma, surgery, burns or severe acne and is more common in non-Caucasians.

Chemical – A substance formed by altering the molecular structure of a natural material or combining two or more elements to form a new substance.

Chemotaxis – Movement or positional change of a cell or organism in response to a chemical agent.

Chloasma – Melanoderma or melasma characterized by irregular brown facial patches, commonly associated with pregnancy, menopause, oral contraceptives, or UV-sensitizing medications.

Cholesterol – A lipid and the most abundant steroid in animal tissues.

Chromosomes – Structures within the cell nucleus containing genes.

Chronic – Symptoms of disorder lasting more than one month.

Colitis – Inflammation of the colon.

Comedogenic – Any agent that may cause comedones; often rated on a 0–3 scale.

Comedones – Dilated hair follicles filled with keratin, squamae and sebum; commonly called blackheads.

Conductor – Material connecting two poles which allows the flow of electrical current.

Connective Tissue – Fibrous tissue that supports and binds structures of the body.

Constitutive Skin Color – Normal skin color generated without radiation or hormonal exposure.

Contaminant – Unwanted organisms or substances such as bacteria, yeast, mold or fungi.

Contraindication – A condition or symptom that makes the use of a treatment inadvisable.

Cornified – Hardened, as in cornified cells of the stratum corneum.

Cosmetic – Topical preparation designed to enhance appearance.

Couperose – Diffuse facial redness including telangiectasias.

Cutaneous – Relating to the skin.

Cyanosis – Bluish discoloration of skin and mucous membranes due to insufficient oxygenation of blood.

Cysts – Severe follicular infections appearing as deep, painful nodules beneath the skin, often resulting in scarring.

Cytochemical – Chemistry of the cell.

Cytoplasm – Fluid part of the cell containing organelles.

Cytotoxicity – Condition involving damage or poisoning of a cell.

D

D&C – Drug and Cosmetic. Colorants approved for use in drugs and cosmetics but not food.

Decongestant – Substance that aids removal of accumulated toxic material via lymphatic drainage.

Dehydration – Excessive transdermal water loss causing flaky, dry, fissured and irritated skin.

Dendrite – Foot-like projection of a cell that receives and transmits impulses.

Dermatology – Medical science of the structure, function and diseases of the skin.

Dermatosis – Nonspecific term for any skin lesion or eruption.

Dermis – Fibrous skin layer beneath the epidermis composed of collagen and elastin.

Dermography – Form of urticaria where wheals appear after skin stroking.

Desquamation – Sloughing of cells from the stratum corneum.

Detergent – Synthetic cleansing agent acting as a surfactant.

Diabetes – Disease characterized by excessive urination, usually referring to diabetes mellitus.

Diapedesis – Migration of cells through blood vessel walls.

Differentiation – Process by which cells acquire specialized functions.

Direct Current – Constant electrical flow in one direction.

Dispersant – Ingredient that evenly distributes other ingredients throughout a product.

Diurnal – Occurring primarily during the day.

Drug – Substance applied or taken internally that alters physiological processes.

Dye – Soluble colorant that colors each molecule of a substance.

E

Eczema – Generic term for acute or chronic inflammatory conditions of the skin, typically erythematous, edematous, papular, vesicular, and crusting; often followed by lichenification and scaling and occasionally by duskiness of the erythema and infrequently hyperpigmentation. Often accompanied by sensations of itching and burning; the vesicles form by intraepidermal spongiosis. Sometimes referred to colloquially as tetter, dry tetter, and scaly tetter. A very common dermatosis, representing almost half of professional dermatitis conditions.

Edema – Accumulation of excess fluid in skin tissue.

Elasticity – Pertains to the capacity of the skin to stretch without losing shape.

Elastin – Connective tissue resembling a net-like sheet of cross-linked fibers composed of protein. A major component of the skin, lungs, ligaments, and large blood vessels.

Elastosis – Degenerative change in elastic tissue, mostly due to excessive sun damage.

Electrocautery – Burning with electric current.

Electrodessication – Process of destroying tissue, usually hair, by removing moisture via electric current.

Electrolysis – Decomposition of a salt or tissue of the body by means of an electric current.

Emollient – Products or ingredients that soften and soothe the skin. Usually oil-soluble substances, though some water-soluble esters may also function as emollients. While often confused with moisturizers, the two functions are different though they may occur simultaneously.

Emulsion – Oil and water components blended together creating one substance.

Endosome – Microscopic membranous sac inside a living cell formed from the cell membrane containing ingested substances.

Enzyme – Protein compounds produced by living organisms acting as catalysts for biochemical reactions. They are not consumed during reactions. In topical skin care, enzymes such as papain and bromelain dissolve keratinized buildup at the skin’s surface.

Ephelis (Freckle) – Yellowish or brownish macules developing on exposed skin, especially in fair-complexioned individuals. Lesions increase with ultraviolet exposure.

Epidermis – Outermost layer of the skin containing stratified and cornified cells, melanin, basal cells, and lipids. Functions as a protective barrier for the dermis.

Epilepsy – Chronic neurological disorder characterized by recurrent seizures caused by excessive neuronal discharge.

Epithelial – Pertaining to epithelium.

Erythema – Inflammatory redness of the skin.

Erythrosis – Exaggerated tendency to blush.

Eschar – Thick, coagulated crust developing after thermal burns or chemical or physical cauterization.

Essential Oils – Volatile oils of natural origin obtained primarily from plants by steam distillation. Used in cosmetics, aromatherapy, medicine, perfumery, and flavoring.

Esters – Compounds formed by reaction of an acid and alcohol. Typically emollients designed to improve spreadability and penetration and resist rancidity.

Eumelanin – Brown-black pigment; true melanin.

Excoriation – Scratch mark or linear break in the skin surface, often covered with blood or serous crusts.

Exfoliate – Removal of dead surface skin using scrubs, peels, enzymes, AHAs, or masques to prevent hyperkeratinization and stimulate renewal.

Extracellular Fluid – Fluid found outside the cell, such as blood and interstitial water.

Extract – Concentrated preparation of natural substances obtained using solvents. Includes fluid, solid, powdered extracts and tinctures.

Exudate – Fluid leaking out of a cell.

F

FCC – Food Chemical Code. Publication listing standards for foods, supplements, and additives used by the food industry.

FD&C – Food, Drug, and Cosmetics. Colorants approved for use in food, drugs, and cosmetics.

Fats – Glycerol esters of fatty acids that are semi-solid or solid at room temperature, derived from botanicals or animal sources.

Fatty Acids – Carboxylic acids derived from fats, including saturated (palmitic, stearic) and unsaturated (oleic, linoleic) acids.

Fibroblast – Cell capable of synthesizing collagen and elastin.

Fixative – High-boiling materials that retard evaporation of volatile components in perfume formulations.

Fixed (Fatty) Oils – Oils similar to fats but liquid at room temperature.

Fluid Extracts – Extracts prepared from botanicals using alcohol-water mixtures to achieve prescribed strength.

Folliculitis – Inflammatory reaction in hair follicles, presenting as papules or pustules.

Formula – Ingredients and percentages composing a product, including manufacturing procedure.

Fragrance – Aromatic blend of essential oils and/or synthetic fragrance materials.

Free Radical – Unstable molecule with an impaired electron that damages cells when exposed to UV radiation, heat, or environmental stress.

Free Radical Scavengers – Antioxidants that help protect the skin from free radical damage and slow aging.

Fungi – Plant-like organisms feeding on organic matter.

Furfur – Flaky epidermal scales, commonly seen on the scalp.

Furuncle – Boil caused by bacterial infection of a hair follicle, forming a painful subcutaneous abscess.

G

Galvanic Current – Direct electrical current.

Gelling Agent – Ingredient that thickens a product into a jelly-like or rigid form.

Glands – Skin contains sudoriferous (sweat) glands and sebaceous (oil) glands that secrete sweat and sebum.

Glossing Agent – Ingredient that disperses other ingredients evenly to produce a glossy appearance.

Glycosides – Sugar-containing compounds that yield sugars upon hydrolysis and are common in plants.

Ground – Large conducting body used as a common return for electrical current.

Ground Substance – Extracellular material of the dermis such as glycosaminoglycans.

Gum Resin – Resin mixed with gums, often containing volatile oils; also known as oleogum resins.

H

HIV – Abbreviation for human immunodeficiency virus.

Hemophilia – Hereditary disease transmitted by women and affecting men. An inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhage, spontaneous or traumatic, due to a defect in the blood coagulating mechanism.

Hepatic – A term referring to the liver biliary secretions.

Herpes – Viral disease marked by groups of watery blisters on the skin or mucous membranes such as the mouth, lips, or genitals.

High Frequency – Alternating current.

Holocrine Gland – A gland that secretes its own cells; the sebaceous gland.

Humectant – Substance that preserves the moisture content in a product, especially in crèmes and lotions. Attracts moisture from many places, including the environment, the product it is in, or from the skin.

Hydrate – To build or add moisture.

Hydrocarbon – Chain of carbon and hydrogen molecules linked together.

Hydrolysis (Hydrolyzed) – Process of making a complex substance into a simpler molecular structure by the uptake of water. Allows for greater penetration and better absorption by the skin.

Hydroscopic – Refers to an ingredient that has the ability to retain and absorb moisture.

Hyperkeratinization (Hyperkeratosis, Keratoderma) – Excessive development of horny structures (thickened skin) caused by lack of adequate exfoliation. Appears as a dull, lifeless complexion and may result in comedones and pimples due to follicular obstruction.

Hyperkeratotic – Excessively producing keratin, resulting in rough, hard skin.

Hyperplasia – Excessive growth of cells.

Hyperproliferate – To excessively reproduce cells, as in psoriasis.

Hypertrichosis – Excessive abnormal growth of hair.

Hypoesthesia – Diminished sensitivity to stimulation; reduced sensitivity to touch.

Hypoallergenic – Products or ingredients less likely to cause an allergic reaction in allergy-prone individuals. Requires Repeat Insult Patch Testing on no fewer than 200 human subjects with positive results.

Hypokeratinization (Hyperkeratosis) – Insufficient development of horny structures (thin skin).

I

Ichthyosis – Congenital disorder of keratinization characterized by dryness and fish-skin-like scaling. Often associated with other defects and distinguishable genetically, clinically, microscopically, and by epidermal cell kinetics. Also called alligator or fish skin.

Infusion – Dilute aqueous extracts containing water-soluble ingredients of botanicals, prepared by extracting with boiling water, such as herbal tea.

Inorganic – Substances that are not hydrocarbons or their derivatives. Usually minerals lacking the structure characteristic of living bodies.

Intercellular Space – Space between cells.

Interstitial Fluid – Fluid spaces between cells or structures.

Intraepidermal – Within the epidermis.

Iontophoresis – Delivery system transferring medicaments via direct electrical current.

Irritant – Substance that predictably produces an adverse response such as redness, swelling, itching, burning or blistering. Not to be confused with allergies.

Ischemia – Lack of blood and oxygen.

Isomer – Chemically identical molecules with different structures and properties.

K

Keloid – Hyperplastic scar tissue.

Keratin – Fibrous protein forming part of the stratum corneum, hair, and fingernails.

Keratolytic – Substances that loosen corneocyte adhesions, allowing cells to slough.

Keratosis (Keratiasis) – Epidermal lesion marked by circumscribed overgrowth of the horny layer.

Keratosis Pilaris – Area of skin marked by overgrowth of horny tissue with an entrapped hair at the center.

Keratosis Senile (Senilis) – Skin disease in elderly individuals characterized by dry brown spots with thickened horny overgrowth; actinic keratosis.

L

Lamellar Bodies – Complex lipids forming part of the corneocyte barrier.

Lentigo – Small melanotic spot unrelated to sun exposure; potentially malignant; freckle.

Leukocyte – Infection-fighting white blood cell such as basophils, neutrophils, monocytes, and eosinophils.

Lipids – Oily substances such as fats and waxes, insoluble in water, forming a protective barrier against moisture loss and foreign invasion.

Lipolytic – Capable of breaking down lipids.

Liposomes – Vesicles formed when phospholipids hydrate in water; used to deliver oil- or water-soluble ingredients into the skin.

Lubricant – Oil or cream designed to provide slip and reduce surface tightness. Slows moisture loss but does not build moisture.

Lymph – Clear fluid from tissues flowing through lymphatic vessels, containing white and few red blood cells.

M

Macrophage – Phagocytic immune cell involved in debris removal.

Macula (Macule) – Small discolored patch that disappears momentarily when pressure is applied.

Malignant – Severe form of illness, often resistant to treatment, such as cancer.

Mast Cell – Cell releasing histamine, causing redness and swelling.

Matte Finish – Even-toned, non-shiny surface quality.

Melanin – Skin pigment deposited in the stratum germinativum and activated by UV exposure.

Melanocytes – Pigment-producing cells in the basal layer of the epidermis.

Melanocytic Nevus (Birthmark) – Circumscribed skin malformation caused by pigmentation or vascularity.

Melanogenesis – Creation of melanin.

Metabolism – Chemical processes that break down substances to release energy or build compounds.

Miconazole – Antifungal agent.

Milium (Milia) – Small white cyst caused by trapped keratin and sebaceous matter.

Mineral – Naturally occurring inorganic substance, usually salts or oxides.

Mitochondria – Organelle responsible for cellular energy production.

Mitosis – Process of cell division.

Moisturizer – Product or ingredient that builds or retains skin moisture.

Molecular Weight – Measurement indicating the size of a chemical compound.

Molluscum Pendulum – Fibrous, flabby skin tumor varying in size.

Monocyte – Macrophage present in the bloodstream.

Mucopolysaccharides – Protein-polysaccharide complexes such as glycosaminoglycans.

Mycosis – Disease caused by fungus or yeast.

N

NDC – National Drug Code. The number code assigned to each manufacturer and/or packer of drugs.

NF – National Formulary. Book that lists the standards of purity as well as assay methods for ingredients used by pharmacists to prepare salves, ointments, and lotions.

Natural – Substances that occur in their unprocessed form. In cosmetics, the term refers to products made from ingredients derived from natural materials that are usually organic in nature.

Neoplasia – Growth of new cells.

Neuritis – Inflammation of a nerve associated with neuralgia, hyperesthesia, anesthesia, paresthesia, paralysis, muscular atrophy in the region supplied by the affected nerve, and with absence of reflexes.

Neuron – Nerve cell.

Nodules – Small mass of rounded or irregular shape. Small, circumscribed solid elevation that usually extends into the deep layers of the skin.

Non-Sensitive – Reduced sensitivity to the environment or other ingredients.

Nucleus – Oval or rounded part of a cell distinct from the cytoplasm. Contains organelles and divides to reproduce the cell. Contains DNA and RNA.

Nutrient – Substance such as a vitamin that provides elements for the ongoing functioning of the body’s metabolic processes.

O

OTC – Over-the-counter drugs. Non-prescription drugs subject to FDA regulations and manufactured, packaged, and distributed according to Federal Law.

Occlusive – Materials such as oils and waxes that cannot be penetrated by water. Form an occlusive shield or film on the skin to slow or prevent moisture evaporation.

Ohm – Measure of electrical resistance.

Opacifying System – System used to make a product opaque or non-clear, such as pearlizing in a cleanser.

Opaque – Opposite of transparent; dense coverage that still allows light penetration.

Organelle – Body within the cytoplasm of a cell with a specialized function.

Organic – Substances that are or have been alive and contain carbon molecules in their chemical structure.

Osteoarthritis – Degenerative joint disease primarily affecting weight-bearing joints such as the knee and hip.

Otitis – Inflammation of the ear.

Oxidation – Chemical reaction in which a molecule gains an atom of oxygen.

P

pH – Power of hydrogen. The amount of hydrogen present determines the acid or alkaline level of a product. On skin, pH refers to the acid mantle, which normally ranges between 4.5 and 6.5.

Papillary Varis – Capillary hemangioma simplex or nevus vascularis. Small pearl-like angioma embedded in the dermis.

Papule – Small, circumscribed, solid elevation involving the epidermis or dermis. May contain trapped sebum and bacteria causing inflammation.

Papulopustules – Small semi-solid skin elevation that rapidly evolves into a pustule.

Pathogenicity – Condition of being able to cause disease.

Permanently Approved Color – Cosmetic color approved by the FDA after safety investigation by a CTFA committee.

Permeable – Allowing substances to flow into or out of a structure, such as fluids moving through a cell membrane by osmosis.

Phaeomelanin – Yellow pigment similar to melanin containing cysteine.

Phospholipid – Lipid containing phosphorus.

Phlyctena – Blister or vesicle filled with transparent serous fluid, such as from severe sunburn or first-degree burns.

Photodamage – Harmful effects of sun exposure causing thickened skin, roughness, and hyperpigmentation.

Photosensitize – To make sensitive to ultraviolet light. Citrus fragrances, antibiotics, and hormones may cause photosensitivity.

Phyto – Pertaining to plants. Includes phytotherapy, phyto oils, and phytoestrogens.

Pigment – Coloring agent in skin or hair.

Pigmentary Spots – Normal or pathological coloration caused by pigment deposits.

Pilosebaceous Apparatus – Structure consisting of hair, follicle, and sebaceous gland.

Pimples – Inflammatory lesions formed when follicles fill with oil, dead cells, and bacteria, leading to rupture and pus formation.

Pituitary Gland – Master gland at the base of the brain controlling hormonal activity.

Pityriasis – Patchy hypopigmentation caused by mild dermatitis and non-inflammatory desquamation.

Pityriasis Versicolor (Tinea) – Tan or brown patches on the trunk appearing white against hyperpigmented skin after UV exposure.

Polarity – Property of having two opposite poles or characteristics.

Polymers – Chains of identical units such as glucose molecules. Efficient delivery systems for lubricants and protectants.

Preservative – Ingredient that prevents growth of bacteria, fungi, yeast, and mold in products.

Proliferation – Growth and reproduction.

Protective Film – Layer of ingredients that adhere to the skin to protect against environmental stress.

Proteoglycan – Component of ground substance.

Provisionally Approved Color – Cosmetic color approved by the FDA pending further safety investigation.

Pruritus – Itching caused by histamine release, dryness, soap residue, aging, or brief contact with water.

Psoriasis – Condition characterized by red, silvery-scaled plaques commonly found on elbows, knees, scalp, and trunk.

Pumice – Lightweight abrasive volcanic stone used to polish hardened skin.

Pus – Fluid product of inflammation containing dead white blood cells and debris.

Pustule – Small circumscribed elevation of skin filled with pus and an inflamed base.

Q
Quantum – Smallest unit of energy.
R
RNA – Ribonucleic acid found in the cell’s nucleic material is responsible for working with the DNA.
Regenerative – Recreation of living material or a renewed functioning. Term used to describe the word “healing” when used in description of an ingredient used in a skin care product.
Regime – Daily routine in the application of skin care products.
Reticular dermis – Layer of the dermis composed of a fine network of cells that make up connective tissue and fibers between the cells. Retinoids – See Vitamin A
Retinyl Palmitate – See Vitamin A
Rhinophyma – Hypertrophy of the nose with follicular dilation, resulting from hyperplasia of sebaceous glands with fibrosis and increased vascularity. Also referred to as hypertrophic rosacea.
Ribosome – Structure found on the rough endoplasmic reticulum that assist in the synthesis of protein in the cell.
Rosacea – Also called “acne rosacea,” rosacea is a chronic inflammation of the skin that causes painful eruptions, usually around the cheek, nose, and at times around the chin area. Characterized by redness, dilation of the blood vessels, and the formation of the papules and pustules. Over time, the skin becomes coarse and the pores enlarged. May be caused by genetic traits, poor digestion and the Demodex mite. Heat, alcohol, extreme temperatures, faulty elimination, hyperacidity, and highly seasoned foods tend to trigger flares.
S
SD Alcohol (SDA) – Specially denatured alcohol. Ethyl alcohol made non-drinkable by adding unpleasant substances. SPF – Sun Protection Factor. Numerical rating on sunscreen and sun blocks that indicate the level of protection from UV radiation. Scars – Fibrous tissue replacing normal tissue destroyed by injury or disease.
Sebaceous Cyst – Pilar or trichilemmal cyst; common cyst of the skin and subcutis containing sebum and keratin, lined by pale, staining, stratified epithelial cells derived from the pilosebaceous apparatus.
Sebaceous Hyperplasia – a disorder of the sebaceous glands in which they become enlarged. These glands are located within the skin and are responsible for secreting an oily substance named sebum. They are commonly associated with hair follicles but they can be found in hairless regions of the skin as well.
Seborrhea – Excessive sebum secretion where skin becomes rapidly oily and shiny with 1-2 hours after cleansing. May also be a result of hyperkeratinization.
Sebum – Semi-liquid oil secreted by the sebaceous apparatus that flows to the skin’s surface.
Secretions – Production by a cell or aggregation of cells (a gland) of a physiologically useful substance and its introduction into the body by direct diffusion or by a duct.
Senile Lentigo – Liver spot; a variably pigmented lentigo occurring on exposed skin of older Caucasians.
Sensitizer – Ingredient that causes the skin to become sensitive to other ingredients or the environment. It also refers to an ingredient that causes the skin to produce an adverse physical reaction such as redness, swelling, blistering or itching.
Sequestrant – Ingredient that releases itself or other ingredients slowly into a product over a period of time. Usually refers to preservatives that have a “time-release” action in maintaining the color, consistency and fragrance.
Sinusitis – Inflammation of a sinus of the skull.
Sloughing – Shedding of an outer layer of hornified tissue from a living structure such as the skin.
Soluble – Ability to dissolve into, or being compatible with another substance.
Soothing – Calming ingredient. Reduces the discomfort of irritated, blemished, burning skin.
Spasm – Involuntary muscular contraction; if painful, usually referred to as a cramp; if violent, a convulsion. Muscle spasm: increased muscular tension and shortness that cannot be released voluntarily and prevents lengthening of the muscles involved. Spasm is due to painful stimuli to the lower motor neuron.
Sphingolipid – Lipid containing a long chain base.
Spider vein – Arterial spider angioma generally found on the face and legs; a red spot producing telangiectasia. Squama – Structure resembling a scale. An epidemic scale made up of thin flat cells.
Stabilizer – An ingredient that makes a product stable, keeping it from losing its viscosity, separating or becoming rancid.
Steatoma – Sebaceous cyst. Subcutaneous tumor of the sebaceous gland in which the contents consist of sebum. Steatoma usually occurs on the scalp, neck and back.
Steroid – A large family of chemical substances comprising many hormones, vitamins, body constituents and drugs. Sterol – A steroid.
Stimulant – An ingredient, usually and herb or vitamin, which quickens or increases body activities such as blood flow, waste removal, cell reproduction or metabolic functions.
Stratum corneum – Flat, cornified (keratinized) skin cells that form a protective outer layer. Also known as the horny later.
Stretch marks – Bands of thin wrinkled skin, initially red but becoming purple and white, occur commonly on the abdomen, buttocks, and thighs at puberty and/or during and following pregnancy. Result from atrophy of the dermis and overextension of the skin.
Subcutaneous – Below the skin.
Substantive – Refers to the ability of an ingredient to be retained in the hair of the skin.
Substrate – Substance an enzyme acts upon.
Sudoriferous (sweat) glands – Tube-like structures (duct) that ends at the skin surface to form the sweat pore. Almost all parts of the body have sweat glands. They regulate body temperature and help eliminate waste products. Controlled by the nervous system.
Sunscreen – Preparation that blocks harmful, burning sunrays.
Surfactant – Abbreviation of the term “surface-active” agent. Wetting agent that reduces the surface tension of oils, grease and other substances allowing them to be broken up into smaller particles to facilitate cleansing and promote easier spreadability and penetration.
Synthetic – Material formed by combining simple element structure. Most parent elements used to manufacture synthetic cosmetic ingredients are of natural origin.

Q

Quantum – Smallest unit of energy.

R

RNA – Ribonucleic acid found in the cell’s nuclear material responsible for working with DNA.

Regenerative – Recreation of living material or renewed functioning. Term often used to describe “healing” when referring to skin care ingredients.

Regime – Daily routine in the application of skin care products.

Reticular Dermis – Layer of the dermis composed of a fine network of cells forming connective tissue and fibers between cells.

Retinoids – See Vitamin A.

Retinyl Palmitate – See Vitamin A.

Rhinophyma – Hypertrophy of the nose with follicular dilation caused by sebaceous gland hyperplasia, fibrosis, and increased vascularity; also known as hypertrophic rosacea.

Ribosome – Structure on the rough endoplasmic reticulum assisting in protein synthesis.

Rosacea – Chronic inflammatory skin condition causing redness, dilation of blood vessels, and papules and pustules, commonly affecting the cheeks and nose. Triggers include heat, alcohol, extreme temperatures, and dietary factors.

S

SD Alcohol (SDA) – Specially denatured alcohol. Ethyl alcohol rendered non-drinkable by the addition of unpleasant substances.

SPF – Sun Protection Factor. Numerical rating indicating the level of protection against ultraviolet radiation.

Scars – Fibrous tissue replacing normal tissue destroyed by injury or disease.

Sebaceous Cyst – Pilar or trichilemmal cyst containing sebum and keratin derived from the pilosebaceous apparatus.

Sebaceous Hyperplasia – Disorder of sebaceous glands characterized by enlargement and increased sebum production.

Seborrhea – Excessive sebum secretion causing skin to become oily and shiny shortly after cleansing.

Sebum – Semi-liquid oil secreted by sebaceous glands that flows to the skin’s surface.

Secretions – Production of physiologically useful substances by cells or glands and their release into the body.

Senile Lentigo – Liver spot; pigmented lesion occurring on sun-exposed skin of older individuals.

Sensitizer – Ingredient that increases skin sensitivity or causes adverse reactions such as redness or itching.

Sequestrant – Ingredient that releases itself or other ingredients slowly over time, often used in preservatives.

Sinusitis – Inflammation of a sinus cavity.

Sloughing – Shedding of outer hornified tissue from the skin.

Soluble – Ability to dissolve into or be compatible with another substance.

Soothing – Calming ingredient that reduces discomfort of irritated or inflamed skin.

Spasm – Involuntary muscular contraction; may be painful or convulsive.

Sphingolipid – Lipid containing a long-chain base.

Spider Vein – Arterial spider angioma producing visible telangiectasia, commonly on the face and legs.

Squama – Scale-like epidermal structure composed of thin, flat cells.

Stabilizer – Ingredient that maintains product consistency and prevents separation or rancidity.

Steatoma – Sebaceous cyst forming a subcutaneous tumor containing sebum.

Steroid – Large class of chemical substances including hormones, vitamins, and drugs.

Sterol – A type of steroid.

Stimulant – Ingredient that increases biological activity such as circulation or metabolism.

Stratum Corneum – Outermost layer of flat, keratinized skin cells forming a protective barrier.

Stretch Marks – Bands of thin wrinkled skin caused by dermal atrophy and overextension.

Subcutaneous – Located beneath the skin.

Substantive – Refers to an ingredient’s ability to be retained on the skin or hair.

Substrate – Substance upon which an enzyme acts.

Sudoriferous (Sweat) Glands – Duct glands that regulate temperature and eliminate waste through sweat.

Sunscreen – Preparation that blocks harmful ultraviolet radiation.

Surfactant – Surface-active agent that reduces surface tension, aiding cleansing and spreadability.

Synthetic – Material formed by combining simple elements, often derived from natural sources.

T

T-Zone – T-shaped area of the face formed by the forehead, nose, and chin. These areas tend to be oilier than other parts of the face.

Tactily – Using the fingertips.

Telangiectasia – Dilation of previously existing small or terminal vessels. Lesion formed by a dilated capillary or terminal artery, most commonly on the skin.

Telomere – Protective DNA sequences at the ends of chromosomes that shorten with each cell division, eventually limiting cell replication and increasing vulnerability to damage.

Texture – Ingredient or product that noticeably smooths and softens the skin’s surface.

Thickener – Ingredient that increases the viscosity of a product.

Thickness of the Skin – Varies by region and individual. Refers to the combined thickness of the epidermis, dermis, and hypodermis. Epidermal thickness ranges from 0.04 mm at the eyelids to 1.5 mm on palms and soles.

Thrombosis – Formation or presence of a blood clot within a vessel that may cause infarction of supplied tissues.

Tincture – Slight infusion of alcohol and water.

Toning – Restoring color and tone to the skin.

Toxic – Poisonous.

Tuberculoses – Communicable disease caused by Mycobacterium tuberculosis, primarily affecting the lungs and characterized by toxic or allergic manifestations.

U

U.S.P. – United States Pharmacopoeia. Book of standards for purity, formulas, and chemical assay methods for drugs.

Ulcers – Lesions on the skin or mucous membranes caused by superficial tissue loss, usually with inflammation.

Ultraviolet – Light wavelengths between visible violet light and x-rays; potentially harmful to the skin.

V

Vacuole – Cavity within the cytoplasm of a cell that may function as a storage or digestive structure.

Varicose Veins – Dilated, enlarged, often painful veins, arteries, or lymphatic vessels.

Vascular – Pertaining to or containing blood vessels.

Vasoconstriction – Constriction or narrowing of blood vessels.

Vesicle – Small elevation of the skin enclosing serous fluid; blister or bulla.

Vialaceous – Purplish discoloration of the skin.

Virulent – Poisonous.

Viscosity – Thickness or thinness of a fluid.

Vitamin A – Bi-polar molecule forming the retinoid family, including retinol, retinal, retinoic acid, and retinyl esters. Retinoids regulate epithelial cell growth and play roles in vision, immune function, bone growth, and cell differentiation.

Vitiligo – Acquired depigmentation disorder characterized by white patches of skin, often symmetrically distributed.

Volt – Measure of electrical pressure.

W

Water-Resistant – Repelling moisture or water; not readily removed by water.

Water-Soluble – Ability to dissolve in water; easily removed with water.

Wetting Agent – Water-soluble ingredient that lowers surface tension, improving spreadability and penetration.

Wood’s Light – Ultraviolet lamp used for skin diagnosis, operating at 320–400 nm.

X

Xanthoma – Disorder of cholesterol metabolism characterized by yellow patches on the skin.