Skincare Glossary

A

AHA (Alpha Hydroxy Acid) — Alpha hydroxy acids are a group of water-soluble acids derived from fruits, milk, and sugar cane. The most common AHAs i…

Antioxidant — Antioxidants are molecules that protect the skin from damage caused by free radicals — unstable atoms generated by UV ra…

Astringent — An astringent is a topical product or ingredient that causes the contraction of skin cells and tissues, temporarily tigh…

Atopic Dermatitis — Atopic dermatitis is a chronic, inflammatory skin condition and the most common form of eczema. It causes dry, itchy, re…

B

Barrier Function — The skin's barrier function refers to the protective role of the outermost layer of the epidermis, the stratum corneum. …

BHA (Beta Hydroxy Acid) — Beta hydroxy acid refers primarily to salicylic acid, an oil-soluble exfoliant that penetrates into pores to dissolve ex…

Broad Spectrum — Broad spectrum is a sunscreen classification indicating that a product protects against both UVA and UVB rays. UVB rays …

C

Ceramides — Ceramides are a family of waxy lipid molecules that occur naturally in the skin and make up about 50% of the lipids in t…

Chemical Exfoliant — A chemical exfoliant is a skincare product that uses acids or enzymes to dissolve the bonds between dead skin cells, pro…

Collagen — Collagen is the most abundant protein in the human body, providing structural support to the skin, bones, tendons, and l…

Comedogenic — Comedogenic describes an ingredient or product that has a tendency to clog pores and contribute to the formation of come…

Comedone — A comedone is a basic acne lesion formed when a hair follicle becomes clogged with dead skin cells, sebum, and sometimes…

Contact Dermatitis — Contact dermatitis is a localized skin inflammation that occurs when the skin comes into direct contact with a substance…

Cystic Acne — Cystic acne is the most severe form of acne, characterized by large, deep, painful, inflamed breakouts that form beneath…

D

Dermatitis — Dermatitis is a general term for skin inflammation, characterized by redness, swelling, itching, and sometimes blisterin…

Dermis — The dermis is the thick middle layer of the skin, located between the epidermis (outer layer) and the hypodermis (subcut…

Desquamation — Desquamation is the natural, ongoing process by which the outermost layer of dead skin cells (corneocytes) sheds from th…

Double Cleansing — Double cleansing is a two-step face washing method that originated in Korean and Japanese skincare routines. The first s…

E

Elastin — Elastin is a highly elastic protein found in the dermis that allows the skin to stretch and snap back to its original sh…

Emollient — An emollient is a type of moisturizing ingredient or product that works by filling in the gaps between skin cells with l…

Emulsifier — An emulsifier is an ingredient that allows two normally immiscible substances — typically oil and water — to mix togethe…

Enzymes — In skincare, enzymes are biological proteins used as gentle exfoliating agents. They work by breaking down the keratin p…

Epidermis — The epidermis is the outermost layer of the skin and serves as the body's primary physical barrier against the environme…

Exfoliation — Exfoliation is the process of removing dead skin cells from the surface of the skin to reveal fresher, smoother skin ben…

F

Fibroblast — Fibroblasts are the primary cells in the dermis responsible for producing collagen, elastin, glycosaminoglycans (like hy…

Fitzpatrick Scale — The Fitzpatrick Scale is a numerical classification system developed by dermatologist Thomas Fitzpatrick in 1975 that ca…

Free Radicals — Free radicals are unstable, reactive molecules with unpaired electrons that damage cells by stealing electrons from othe…

G

Glycerin — Glycerin (also called glycerol) is one of the most effective and widely used humectant ingredients in skincare. It is a …

Glycolic Acid — Glycolic acid is the smallest and most widely researched alpha hydroxy acid (AHA), derived from sugar cane. Its small mo…

H

Humectant — A humectant is a type of moisturizing ingredient that attracts and binds water molecules from the environment and from d…

Hyaluronic Acid — Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan found throughout the body's connective tissues, with the…

Hyperpigmentation — Hyperpigmentation is a common skin condition where patches of skin become darker than the surrounding areas due to exces…

Hypodermis — The hypodermis, also called the subcutaneous layer or subcutis, is the deepest layer of the skin lying below the dermis.…

I

Inflammation — Inflammation is the immune system's response to injury, infection, or irritation, characterized by redness, swelling, he…

Irritant — An irritant is any substance that causes a non-allergic inflammatory reaction when it comes into contact with the skin. …

J

Jojoba Oil — Jojoba oil is a liquid wax ester extracted from the seeds of the jojoba plant (Simmondsia chinensis), native to the sout…

K

Keratin — Keratin is a tough, fibrous structural protein that is the primary component of the outermost layer of skin (stratum cor…

Keratinocyte — Keratinocytes are the predominant cell type in the epidermis, making up approximately 90% of epidermal cells. They are p…

L

Lactic Acid — Lactic acid is an alpha hydroxy acid (AHA) derived from milk that serves as a gentle chemical exfoliant. It has a larger…

LED (Light Emitting Diode) — In skincare, LED refers to light emitting diode technology used to deliver specific wavelengths of light to the skin. Di…

Lipid Barrier — The lipid barrier (also called the lipid matrix or lipid bilayer) is the intercellular 'mortar' between the corneocytes …

M

Melanin — Melanin is the natural pigment produced by melanocytes in the basal layer of the epidermis that gives skin, hair, and ey…

Melanocyte — Melanocytes are specialized cells located in the basal layer of the epidermis that produce melanin, the pigment responsi…

Microbiome — The skin microbiome refers to the vast community of microorganisms — including bacteria, fungi, viruses, and mites — tha…

Milia — Milia are small, white or yellowish, dome-shaped bumps that appear on the skin when keratin (a protein) becomes trapped …

Moisturizer — A moisturizer is a skincare product designed to hydrate the skin and prevent water loss by combining three types of mois…

N

Niacinamide — Niacinamide (also known as nicotinamide) is a form of vitamin B3 that has become one of the most versatile and popular a…

Non-Comedogenic — Non-comedogenic is a term used to describe skincare and cosmetic products that are formulated to be less likely to clog …

O

Occlusives — Occlusives are a category of moisturizing ingredients that work by forming a physical barrier on the skin's surface to p…

Oxidative Stress — Oxidative stress occurs when there is an imbalance between the production of free radicals (reactive oxygen species) and…

P

Peptides — Peptides are short chains of amino acids (typically 2-50 amino acids long) that serve as building blocks for proteins li…

pH Balance — pH (potential of hydrogen) is a measure of acidity or alkalinity on a scale of 0 to 14, with 7 being neutral. Healthy sk…

Photobiomodulation — Photobiomodulation is the use of specific wavelengths of light — typically red and near-infrared — to stimulate cellular…

PIE (Post-Inflammatory Erythema) — Post-inflammatory erythema (PIE) refers to the flat, pink to red or purple marks left on the skin after an inflammatory …

PIH (Post-Inflammatory Hyperpigmentation) — Post-inflammatory hyperpigmentation (PIH) is a type of hyperpigmentation that occurs as the skin heals from inflammation…

Pore — Pores are the tiny openings on the skin's surface through which hair follicles reach the surface and through which sebum…

Propolis — Propolis is a natural, resinous substance produced by honeybees from tree buds, sap flows, and other botanical sources. …

R

Red Light Therapy — Red light therapy uses wavelengths between 620-700 nanometers to penetrate the skin and stimulate mitochondrial energy p…

Retinoid — Retinoids are a class of chemical compounds derived from vitamin A that are widely considered the gold standard in anti-…

Retinol — Retinol is the most popular and widely available over-the-counter form of vitamin A (retinoid) used in skincare. It is a…

Rosacea — Rosacea is a chronic, inflammatory skin condition that primarily affects the central face — cheeks, nose, chin, and fore…

S

Salicylic Acid — Salicylic acid is a beta hydroxy acid (BHA) derived from willow bark that is one of the most effective and widely used i…

Sebaceous Gland — Sebaceous glands are small, oil-producing glands attached to hair follicles throughout the body (except on the palms and…

Sebum — Sebum is the waxy, oily substance produced by sebaceous glands to lubricate and waterproof the skin and hair. It is comp…

Sensitized Skin — Sensitized skin is a condition where the skin has become temporarily reactive, irritated, and easily aggravated due to e…

Skin Cycling — Skin cycling is a skincare method popularized by dermatologist Dr. Whitney Bowe that involves rotating active ingredient…

SPF — SPF stands for Sun Protection Factor, a numerical rating that indicates how much longer a sunscreen allows you to stay i…

Stratum Corneum — The stratum corneum is the outermost sublayer of the epidermis and the body's first physical barrier against the externa…

Sunscreen — Sunscreen is a topical product that protects the skin from the harmful effects of ultraviolet (UV) radiation, which caus…

T

Toner — A toner is a liquid skincare product applied after cleansing and before serums and moisturizers. Historically, toners we…

Transepidermal Water Loss (TEWL) — Transepidermal water loss (TEWL) is the process by which water passes from the dermis through the epidermis and evaporat…

Tretinoin — Tretinoin (all-trans retinoic acid) is the most potent and well-researched prescription retinoid, available under brand …

U

Urea — Urea is a naturally occurring compound found in the skin as part of the natural moisturizing factor (NMF) — the collecti…

UVA — UVA (Ultraviolet A) rays are the longest wavelength of ultraviolet radiation (320-400 nm) emitted by the sun. They accou…

UVB — UVB (Ultraviolet B) rays are medium-wavelength ultraviolet radiation (280-320 nm) that primarily affects the epidermis, …

V

Vitamin C (Ascorbic Acid) — Vitamin C (L-ascorbic acid) is one of the most researched and effective antioxidant ingredients in skincare. It neutrali…

Vitamin E (Tocopherol) — Vitamin E (tocopherol) is a fat-soluble antioxidant that occurs naturally in the skin's sebum and plays a critical role …

W

Whiteheads — Whiteheads (closed comedones) are a type of non-inflammatory acne that appears as small, flesh-colored or white bumps on…

Witch Hazel — Witch hazel is a plant-derived ingredient extracted from the bark and leaves of the Hamamelis virginiana shrub, native t…

X

Xeroderma — Xeroderma is the medical term for abnormally dry skin, characterized by roughness, tightness, flaking, scaling, cracking…

Z

Zinc (topical) — Topical zinc refers to various zinc compounds used in skincare for their anti-inflammatory, antimicrobial, wound-healing…

Zinc Oxide — Zinc oxide is a mineral (inorganic) sunscreen ingredient that provides broad-spectrum protection against both UVA and UV…