Skincare, defined.

AHAs, or alpha hydroxy acids, are water-soluble acids such as glycolic and lactic acid, used in skincare for chemical exfoliation. They loosen dull surface cells so skin looks smoother. They can sting and raise sun sensitivity, so patch test and use sunscreen.

BHAExfoliationPatch test

An ampoule is a small-batch, concentrated Korean skincare product, usually lighter than a cream and richer in chosen ingredients than an essence. It is used after toner or essence, in a few drops or pumps, before moisturiser, as a focused extra step.

Learn moreEssenceSerumLayering

Azelaic acid is a dicarboxylic acid found naturally in some grains, such as barley and wheat, and used in skincare in gels, creams and cleansers. It is often chosen for skin that looks uneven or congested. Patch test first, as mild tingling is possible.

Learn moreHyperpigmentationNiacinamidePatch test

BHA, or beta hydroxy acid, usually means salicylic acid. It is oil-soluble, so it can work inside pores and is used in skincare to exfoliate and refine the look of congested areas. It can dry skin, so start slowly and patch test.

AHAExfoliationSebum

Bifida ferment lysate is a skincare ingredient made by fermenting Bifidobacterium bacteria and breaking the cultured cells into fragments. It is used in essences and serums to support skin that feels stressed, and is valued for its fermented, Korean skin science heritage.

Learn moreLysateFerment filtrateEssence

Broad spectrum describes a sunscreen that protects against both UVB and UVA rays, not just the rays that cause sunburn. In some markets the label has a defined test behind it. Checking for a PA rating is another way to see UVA coverage.

Learn moreUVAUVBPA ratingSPF

Centella asiatica is a leafy plant used in traditional practice across Asia and now common in K-beauty, where it is nicknamed cica. Its extract and compounds such as madecassoside are used in skincare to help skin feel calm and comfortable.

Learn moreMadecassosideSkin barrierK-beauty

Ceramides are lipids, or fats, that occur naturally in the outer layer of skin, where they help hold cells together as part of the skin barrier. Skincare products add them to help skin feel soft and comfortable, especially when it is dry or tight.

Learn moreSkin barrierEmollientTransepidermal water loss

Chemical filters, also called organic filters, are carbon-based sunscreen ingredients that absorb UV light in the skin's upper layer and release it as a small amount of heat. They are usually lightweight and clear on skin, leaving little to no white cast.

Mineral filterHybrid sunscreenWhite cast

Comedogenic describes an ingredient or product that is thought to be more likely to clog pores and form comedones, or blackheads and whiteheads. It is a general term, not a guarantee, because how skin responds depends on the whole formula and the person.

SebumDouble cleansingDermatologist

Dry skin is a skin type that produces less oil, while dehydrated skin is a temporary state of lacking water that any skin type can have, including oily skin. Dehydrated skin often looks dull or feels tight, and humectants help it feel more hydrated.

HumectantSebumTransepidermal water loss

A dermatologist is a medical doctor who specialises in conditions of the skin, hair and nails. They are the right person to see for persistent acne, rashes, sudden changes, scalp concerns or anything painful, rather than relying on cosmetic products or guesswork.

Patch testScalp microbiome

Double cleansing is a two-step Korean cleansing routine. An oil or balm-based cleanser comes first to lift sunscreen, sebum and makeup, then a water-based gel cleanser follows to rinse away the rest. It is most useful on days you wear sunscreen or makeup.

Learn moreGel cleanserSPFSebum

An emollient is an ingredient that softens and smooths the skin by filling small gaps between surface cells. Examples include plant oils, squalane and fatty alcohols. Emollients make skin feel supple and are a main part of most moisturisers.

HumectantOcclusiveCeramides

An emulsion, in Korean skincare, is a light, fluid moisturiser that sits between an essence and a cream. It is made by blending water and oil components, and suits humid weather or oily skin, or as a first layer of moisture under a cream.

EssenceLayeringHumectant

An essence is a watery, lightweight Korean skincare step used after cleansing or toner. It carries hydrating and conditioning ingredients and helps skin feel soft and ready for the products that follow. It is lighter than a serum and is often patted in by hand.

Learn moreTonerSerumLayering

Exfoliation is the removal of dead cells from the skin's surface, either physically with scrubs or chemically with acids such as AHAs and BHAs. It can make skin look smoother, but overdoing it can leave skin sensitive, so most people need it only occasionally.

AHABHAPatch test

A ferment filtrate is the liquid left after a yeast, fungus or bacteria is grown in a nutrient medium and the live cells are filtered out. It contains by-products of fermentation and is used in K-beauty essences and serums to condition skin.

Learn moreLysateGalactomyces ferment filtrateSaccharomyces ferment filtrate

A formulation target is the planned concentration of an ingredient that a brand aims for while a product is still in development. It is not the final percentage. The finished amount can change after stability and safety testing, so targets should not be read as promises.

Learn moreINCIFragrance-free

Fragrance-free means a product has no added fragrance or perfume ingredients meant to give it a scent. It is different from unscented, which can still contain masking agents. Plant extracts may still have a natural smell, so always check the ingredient list.

INCIPatch test

Galactomyces ferment filtrate is the liquid produced when the yeast-like fungus Galactomyces is fermented and then filtered. It is a popular ingredient in K-beauty essences, where it is used to help skin look smoother, brighter and more even.

Learn moreFerment filtrateSaccharomyces ferment filtrateEssence

A gel cleanser is a water-based face wash with a clear, jelly-like texture that lathers lightly. It rinses off easily and suits oily, combination and humid-weather routines. As the second step of double cleansing, it removes what the oil cleanser has loosened.

Learn moreDouble cleansingSebumpH of skincare

Glass skin is a K-beauty ideal of skin that looks smooth, even and softly reflective, as if lit from within. It describes a look rather than a skin type, and is pursued through hydration, gentle routines and daily sun protection, not one product.

Learn moreK-beautyLayeringSPF

Green tea extract comes from the leaves of Camellia sinensis and contains plant compounds called polyphenols, including catechins. It is used in skincare as an antioxidant ingredient to help protect skin from everyday environmental stress, and to help skin feel fresh.

Learn moreNiacinamideRice water

A humectant is an ingredient that attracts and holds water, helping the outer layer of skin feel hydrated. Glycerin, hyaluronic acid and polyglutamic acid are common examples. Humectants work best when followed by a moisturiser that keeps that water from escaping.

Hyaluronic acidPolyglutamic acidOcclusiveEmollient

Hyaluronic acid is a sugar-based molecule found naturally in skin that can hold a large amount of water. In skincare, it and its salt form, sodium hyaluronate, act as humectants that help skin look plump and feel hydrated.

HumectantPolyglutamic acidDehydrated vs dry skin

A hybrid sunscreen combines mineral filters, such as zinc oxide or titanium dioxide, with chemical filters in one formula. The blend can give broad UV coverage with a lighter feel and a lower chance of white cast than a purely mineral formula.

Learn moreMineral filterChemical (organic) filterWhite cast

Hyperpigmentation describes patches of skin that look darker than the skin around them, because of extra melanin in that area. It can show as spots, marks or shadows and is common on deeper skin tones. For any new or changing mark, see a doctor.

Learn moreSPFIron oxides (tinted sunscreen)Dermatologist

INCI stands for International Nomenclature of Cosmetic Ingredients, the standard naming system used on skincare ingredient lists worldwide. It lets you compare products by the same names, in order of concentration, so you can spot ingredients you want or want to avoid.

Fragrance-freeFormulation target

Iron oxides are mineral pigments used in tinted sunscreens and makeup to add colour. They also help block visible light, which matters for people concerned about dark marks. A good shade match reduces the grey cast that plain mineral filters can leave on deeper skin.

Learn moreWhite castMineral filterHyperpigmentation

K-beauty, short for Korean beauty, is an approach to skincare that favours gentle cleansing, layers of light hydration, daily sun protection and consistent routines. It is known for fermented and plant ingredients and for texture-led, easy-to-wear formulas.

Learn moreGlass skinLayeringDouble cleansing

Layering is the practice of applying skincare products one after another, usually from thinnest to thickest texture. A typical order is cleanser, toner, essence, serum, moisturiser, then sunscreen in the morning. Thin layers absorb better than a few heavy ones.

Learn moreTonerEssenceSerum

A lysate is the material left when cells, such as cultured bacteria or yeast, are broken open and their contents released. In skincare it appears in ingredient names such as bifida ferment lysate, and is used to condition skin within fermented formulas.

Learn moreFerment filtrateBifida ferment lysate

Madecassoside is a purified compound found in Centella asiatica, the plant behind cica skincare. It is used in creams, toners and serums to help skin feel calm and comfortable, particularly skin that is easily flushed or sensitive to weather.

Learn moreCentella asiatica (cica)Skin barrier

Mineral filters are zinc oxide and titanium dioxide, ingredients that sit on the skin's surface and reflect or scatter UV light. They are gentle and work immediately, but older or less refined versions can leave a white cast, especially on deeper skin tones.

Chemical (organic) filterHybrid sunscreenWhite cast

Niacinamide is a form of vitamin B3 widely used in skincare. It supports the skin barrier, helps skin look more even and refines the look of pores. It is generally well tolerated, though higher strengths can cause flushing in some people, so patch test.

Learn moreSkin barrierHyperpigmentationPatch test

An occlusive is an ingredient that forms a protective film on the skin to slow water loss. Petrolatum, waxes and some butters are examples. Occlusives are usually the last layer of moisture and are most helpful in dry air, such as winter or air-conditioned rooms.

HumectantEmollientTransepidermal water loss

The PA rating is a Japanese-origin system, now common in Asian sunscreens, that indicates the level of UVA protection. More plus signs, from PA+ to PA++++, mean stronger UVA protection. It is read alongside SPF, which relates to UVB.

SPFUVABroad spectrum

A patch test is a small trial of a new product on a limited area, such as the inner forearm or behind the ear, before using it on the face. Apply it for a day or two and watch for redness, itching or stinging. Stop use if any appear.

Fragrance-freeDermatologist

The pH of a skincare product is a number from 0 to 14 that shows how acidic or alkaline it is. Skin's surface is slightly acidic, around 4.5 to 5.5, so many gentle cleansers and toners are formulated near that range to feel comfortable.

Gel cleanserSkin barrierToner

Polyglutamic acid, often written as PGA, is a large water-loving molecule produced by bacterial fermentation, as in the Japanese food natto. It is used as a humectant that forms a soft, moisture-holding film on skin, often paired with hyaluronic acid.

Learn moreHumectantHyaluronic acidFerment filtrate

Propolis is a resin-like substance that bees make from plant sap and use to seal their hives. In skincare, propolis extract is valued for its conditioning, comforting feel. People with bee product or pollen allergies should avoid it, and a patch test is wise.

Learn morePatch testK-beauty

Reapplication means putting on more sunscreen during the day, because wear, sweat, rubbing and time reduce its protection. The usual advice is to reapply about every two hours of sun exposure, and after swimming or heavy sweating, even over makeup.

Learn moreSPFUVADouble cleansing

Rice bran is the outer layer of the rice grain that is removed when rice is polished. Rice bran extract and oil are used in skincare for their conditioning, softening feel and natural plant lipids, which suit lightweight cleansers and moisturisers.

Learn moreRice waterEmollient

Rice water is the milky liquid left after soaking or rinsing rice, a long-standing beauty tradition across Asia. In skincare, fermented or processed rice water is used for its mild, softening feel, and it appears in toners, essences and hair care.

Learn moreRice branFerment filtrateToner

Saccharomyces ferment filtrate is the liquid left after a yeast from the Saccharomyces family, the same genus used in baking and brewing, is fermented and filtered. It is used in K-beauty essences to help skin feel soft, hydrated and smooth.

Learn moreFerment filtrateGalactomyces ferment filtrateEssence

The scalp microbiome is the community of microorganisms, including bacteria and yeasts, that naturally lives on the scalp. Researchers are still learning about it, and scalp care products aim to be gentle so the scalp feels clean and comfortable, not stripped.

Learn moreSebumDermatologistSkin barrier

Sebum is the natural oil produced by sebaceous glands in the skin and scalp. It helps keep skin soft and protected, but too much can make skin look shiny or hair feel greasy. Heat, humidity and hormones all affect how much the skin makes.

Gel cleanserComedogenicScalp microbiome

A serum is a lightweight, concentrated skincare product designed to deliver a higher amount of chosen ingredients than a moisturiser. It is applied after cleansing, toner or essence and before moisturiser, in a small amount, and often targets a single skin goal.

Learn moreEssenceAmpouleLayering

The skin barrier is the outermost layer of skin, made of cells held together by lipids such as ceramides. It helps keep water in and irritants out. When it is weak, skin can feel tight, dry or easily stung, so gentle routines help support it.

Learn moreCeramidesTransepidermal water losspH of skincare

Skin cycling is a routine plan that rotates products across a repeating cycle of nights, for example an exfoliating night, a night with another active, then rest nights focused on moisturiser. The aim is to space out strong ingredients and give skin recovery time.

ExfoliationLayeringPatch test

Snail secretion filtrate, often called snail mucin, is a filtered liquid collected from snails, then processed for cosmetic use. It is a K-beauty ingredient used in essences and creams to help skin feel soft, hydrated and bouncy. It is not suitable for vegans.

Learn moreHumectantK-beautyEssence

Snow mushroom, or tremella, is a pale, jelly-like fungus whose polysaccharides are used in skincare as a plant-based humectant. Its extract holds a lot of water and gives a soft, cushiony finish, and it is often compared with hyaluronic acid.

Learn moreHumectantHyaluronic acidPolyglutamic acid

SPF, or sun protection factor, is a number showing how well a sunscreen protects against UVB rays, which cause sunburn. Higher numbers give more protection, though no sunscreen blocks everything. SPF says little about UVA, which is why PA ratings matter too.

Learn moreUVBPA ratingReapplication

Tinosorb M is a modern hybrid sunscreen filter that both absorbs and scatters UV light. It is used in particle form, and protects across UVB and much of the UVA range. Its larger particles help formulas feel light with less visible white cast.

Hybrid sunscreenUVAWhite cast

A toner, in Korean skincare, is a thin, watery step used after cleansing to rebalance the skin's surface and prepare it for later products. Modern toners are hydrating rather than stripping, and are often patted in with the hands to help skin feel soft.

Learn moreEssencepH of skincareLayering

Transepidermal water loss, or TEWL, is the amount of water that passes from deeper layers of skin out into the air through the skin's surface. A healthy barrier keeps it low. Dry air, harsh cleansing and a weakened barrier can raise it.

Skin barrierOcclusiveCeramides

UVA rays are the longer wavelengths of ultraviolet light. They reach deeper into skin, pass through clouds and window glass, and contribute to skin ageing and pigmentation. Broad spectrum sunscreens and PA ratings show how well a product covers UVA.

UVBPA ratingBroad spectrum

UVB rays are the shorter, more energetic wavelengths of ultraviolet light and the main cause of sunburn. They are strongest around midday and in summer, and the SPF number on a sunscreen shows how much UVB protection the product offers.

UVASPFBroad spectrum

White cast is the pale, chalky or greyish film that some sunscreens, particularly mineral ones, leave on skin. It is most visible on deeper skin tones. Newer filters, finer particles and tinted formulas are designed to reduce it.

Learn moreMineral filterIron oxides (tinted sunscreen)Tinosorb M