Ingredient Glossary

INCI: Each form is listed under its own INCI name, for example Sodium Hyaluronate, Hydrolyzed Hyaluronic Acid, Sodium Hyaluronate Crosspolymer

8D hyaluronic acid is a humectant raw material: a blend of eight forms of hyaluronic acid that differ in molecular weight and type, designed to hold moisture in different layers of the skin. It does not appear on the label as a single name.

Because the forms differ in molecular weight, they also differ in how they pass into the skin; the aim is to spread the humectant effect from the surface to the upper layers without depending on a single molecule. The visible result is skin that feels more hydrated and plump.

Read in the guide →Related: Hyaluronic acid, INCI (ingredient list), HumectantSources: [1] [2]

INCI: Acetyl Hexapeptide-8

Acetyl hexapeptide-8, sold under the trade name Argireline™, is a synthetic peptide from the group of peptides that affect nerve signalling, used in formulas for the look of expression lines. On the label it appears as Acetyl Hexapeptide-8.

In the laboratory it has been shown to weaken the nerve signalling associated with muscle contraction; reviews summarise studies that report differences in wrinkle depth, elasticity and hydration measurements. It is used to help soften the look of expression lines.

Read in the guide →Related: Peptide, Matrixyl™ 3000, Copper peptide (GHK-Cu)Sources: [3] [4]

INCI: Charcoal Powder

Activated charcoal is an ingredient that has long been used as an antidote in poisoning and has become common in recent years in cosmetic products such as cleansers and soaps. On the label it appears as Charcoal Powder, and it can give a product its black colour.

A dermatology review states that the claims made for activated charcoal products are not supported by evidence from human studies, that there is no evidence of an exfoliating or anti-ageing effect, and that it is generally considered safe. In Smooth Me All Night it is a supporting ingredient that gives the formula its name and colour.

Read in the guide →Related: Niacinamide (vitamin B3), AHA (alpha hydroxy acids), BHA (beta hydroxy acids), ComedogenicSources: [5]

Active concentration is a statement that shows an ingredient's share of the formula as a percentage: in a serum labelled 10% niacinamide, a tenth of the formula is niacinamide. The effect does not depend on concentration alone.

Concentration is the starting point for comparing products; with acids, the pH, whether the product is rinsed off and how often it is used also change the result. A higher concentration can also increase the likelihood of irritation.

Read in the guide →Related: INCI (ingredient list), pH (skin and product pH), Niacinamide (vitamin B3), CaffeineSources: [6] [7] [8]

AHAs (alpha hydroxy acids) are a group of exfoliating acids that help dead cells shed from the skin's surface. Glycolic and lactic acid are the examples most often used in cosmetics; on the label they appear as Glycolic Acid and Lactic Acid.

According to the FDA, products containing AHAs are marketed to soften the look of fine lines, make texture and tone look more even and unclog pores. The degree of exfoliation is determined by the type of AHA, its concentration, the product's pH and the rest of the formula, taken together.

Read in the guide →Related: BHA (beta hydroxy acids), PHA (polyhydroxy acids), Glycolic acid, Lactic acid, Exfoliation, pH (skin and product pH)Sources: [6] [9] [7] [10]

INCI: Allantoin

Allantoin is a skincare ingredient used in soothing formulas to support skin comfort, usually as a supporting ingredient rather than a key active. In Turkish it is also written “alantoin”.

In a study of facial skincare products marketed for sensitive skin, it was one of the most frequently used ingredients, but it was not tested separately in volunteers with sensitive skin. In a laboratory study, it was part of a blend – with bisabolol, dexpanthenol and a liquorice derivative – that reduced a UVB-induced inflammatory marker.

Read in the guide →Related: Bisabolol, Panthenol (provitamin B5), Sensitive skin, Liquorice root extractSources: [11] [12]

INCI: Alpha-Arbutin

Alpha arbutin is the glycoside form of hydroquinone bound to glucose, used in formulas that target the look of dark spots and uneven tone. One review summarises studies on its antioxidant properties and its effect on melanin synthesis.

It helps reduce the look of dark spots, uneven tone and dark post-blemish marks. It is often combined with tranexamic acid and niacinamide in the same formula.

Read in the guide →Related: Tranexamic acid, Niacinamide (vitamin B3), SPF (sun protection factor), PhotoageingSources: [13] [14] [15]

Antioxidants are a group of substances that help limit oxidative damage by scavenging the free radicals that factors such as sunlight create in the skin. In skincare, vitamin C, vitamin E and caffeine are among the examples known for their antioxidant properties.

Antioxidants are used in formulas that target dullness and the look of uneven tone linked to the cumulative effects of the sun. One review states that vitamin C recycles vitamin E and works with it against oxidative damage.

Read in the guide →Related: Vitamin C (ascorbic acid), Ethyl ascorbic acid, Tocopherol (vitamin E), Photoageing, CaffeineSources: [16] [17] [18] [19]

INCI: Azelaic Acid

Azelaic acid is a saturated dicarboxylic acid with nine carbon atoms, used in cosmetics for the look of dark spots, redness and post-blemish marks. In nature it is also produced by Malassezia yeast.

Reviews describe keratinisation-regulating, melanin-reducing, antioxidant and soothing properties. This is why it appears in formulas that target the look of uneven tone, reddish marks and rough texture.

Read in the guide →Related: Potassium azeloyl diglycinate, Niacinamide (vitamin B3), Tranexamic acid, Sensitive skinSources: [20] [21] [22]

INCI: Adansonia Digitata Pulp Extract

Baobab extract is a plant extract prepared from the fruit pulp of the baobab tree (Adansonia digitata), which grows in Africa, and used in eye-area and peptide formulas. On the label it appears as Adansonia Digitata Pulp Extract.

A food chemistry study identified sugars, amino acids, organic acids, phenolic compounds and fatty acids in baobab fruit pulp and leaves. Our sources include no human study testing the effect of this composition on the skin; this is why no standalone result is promised for the extract.

Read in the guide →Related: Caffeine, Matrixyl™ 3000, Gentian root extractSources: [23]

BHAs (beta hydroxy acids) are a group of exfoliating acids that help dissolve dead-cell build-up on the skin's surface and in the pore opening. According to the FDA, the BHA most commonly used in cosmetics is salicylic acid; chemists, however, do not regard salicylic acid as a true BHA.

BHAs are used mainly for the look of blackheads and clogged pores; unlike AHAs, their effect reaches into the pore opening as well as the surface. On labels they mostly appear as Salicylic Acid, sometimes under related names such as sodium salicylate or willow extract.

Read in the guide →Related: Salicylic acid, AHA (alpha hydroxy acids), Comedogenic, Sebaceous filaments, ExfoliationSources: [24] [25] [26]

INCI: Bisabolol

Bisabolol is a single plant molecule isolated from German chamomile and thought to be soothing; it is not the same as chamomile extract. It is added to many product types, from moisturisers to sunscreens.

It is thought to have soothing and calming properties; in a laboratory study, it was part of a blend – with allantoin, dexpanthenol and a liquorice derivative – that reduced a UVB-induced inflammatory marker. Human studies are limited.

Read in the guide →Related: Allantoin, Centella asiatica (CICA), Sensitive skin, Patch test (inner forearm)Sources: [27] [12] [11]

Blue light is the short-wavelength, high-energy end of visible light (400–700 nm), which is why it is also called HEV (high-energy visible) light. About half of the sunlight that reaches the earth is visible light.

Studies show that visible light can cause more intense and longer-lasting pigmentation than UVA1 in darker skin (phototypes IV–VI), and redness together with UVA1 in lighter skin. Our sources contain no data on the effect of screen light on the skin.

Read in the guide →Related: UVA and UVB, Mineral (physical) filter, Photoageing, SPF (sun protection factor)Sources: [28] [29] [30] [31]

Broad spectrum is a label term showing that a sunscreen protects against both UVA and UVB rays; in the US its use is tied to FDA testing standards.

According to the AAD, a broad-spectrum sunscreen helps prevent sunburn and premature skin ageing by protecting against UVA (ageing) and UVB (burning) rays. The FDA requires a warning on products that are not broad spectrum or have an SPF below 15.

Read in the guide →Related: SPF (sun protection factor), UVA and UVB, PA (Protection Grade of UVA), Chemical (organic) filterSources: [30] [32] [33]

INCI: Caffeine

Caffeine is an alkaloid known for its antioxidant properties; it is used in eye-area products to help reduce the look of temporary puffiness. On the label it appears as Caffeine.

It helps reduce the look of temporary under-eye puffiness that is more noticeable in the morning. Its effect on dark circles depends on their cause: for pigment-related circles, the basic step is sun protection; it does not change shadowing or under-eye bags that set in with age.

Read in the guide →Related: Baobab extract, Gentian root extract, PAO (period after opening), Active concentration, AntioxidantSources: [19] [34] [35] [36]

INCI: Centella Asiatica Extract

Centella asiatica (gotu kola) is a plant whose main constituents are asiaticoside, madecassoside, asiatic acid and madecassic acid, used in cosmetics as a supporting ingredient in soothing formulas. On the label it appears as Centella Asiatica Extract.

It is found in formulas that aim to support skin comfort. One review summarises the plant's long traditional use and laboratory findings; controlled data on its cosmetic effect, however, are limited.

Read in the guide →Related: Allantoin, Bisabolol, Sensitive skin, Niacinamide (vitamin B3)Sources: [37] [11]

INCI: Ceramide NP (in s'hevec products)

A ceramide is a lipid molecule that, together with cholesterol and free fatty acids, forms the intercellular lipids in the skin's top layer and is a core part of the barrier that limits water loss. On the label it appears under letter-coded names such as Ceramide NP.

It supports the barrier and helps limit water loss from the skin's surface. One review highlights the role of ceramides in the barrier and the importance of formulating them correctly in skincare products.

Read in the guide →Related: Skin barrier, TEWL (transepidermal water loss), Natural moisturising factor (NMF), EmollientSources: [38] [39] [40]

A chemical (organic) filter is a UV filter made from carbon-based compounds that works in sunscreens by absorbing UV rays. According to the AAD, a sunscreen that does not contain titanium dioxide or zinc oxide is a chemical sunscreen.

Different filters have different absorption ranges; according to one review, newer-generation, large-molecule UVB-UVA filters offer better protection in the UVA band. The US-approved actives listed by the AAD include avobenzone and octocrylene, as well as bemotrizinol, whose first products reached US shelves in 2026; bemotrizinol has been approved in Europe since 2000.

Read in the guide →Related: Hybrid sunscreen, Mineral (physical) filter, Broad spectrum, SPF (sun protection factor)Sources: [30] [41] [32]

A chemical peel is an exfoliation method that aims to take off the skin's top layer in a controlled way using acids at relatively high concentrations; it ranges from rinse-off products used at home to in-clinic procedures.

It supports a renewed, radiant look of the skin's surface and helps reduce the look of uneven tone. According to the FDA, the more serious reactions reported with AHA products are seen most often with peel-type products, which exfoliate most intensively.

Read in the guide →Related: AHA (alpha hydroxy acids), BHA (beta hydroxy acids), Exfoliation, Patch test (inner forearm)Sources: [6] [24] [42] [9]

Comedogenic is a term for the tendency of an ingredient or product to cause plugs (comedones) to form in the pore opening. A comedone is a plug formed by a build-up of sebum and dead cells; a blackhead is its open form.

The concept developed as certain ingredients became associated with comedone formation, and the first ingredient lists were drawn up using animal models. A human study with finished products showed that products containing ingredients considered comedogenic are not always comedogenic.

Read in the guide →Related: Non-comedogenic, Sebaceous filaments, Salicylic acid, BHA (beta hydroxy acids), Activated charcoalSources: [43] [44]

INCI: Copper Tripeptide-1

Copper peptide (GHK-Cu) is a complex of copper with the GHK peptide, which is made up of three amino acids (glycine-histidine-lysine). On the label it appears as Copper Tripeptide-1, and it is used in products for the look of fine lines.

Cell studies show potential for the look of wrinkles; human studies on GHK-Cu itself, however, are few. Because it dissolves readily in water, its passage into the skin depends on the formula.

Read in the guide →Related: Peptide, Ceramide, Ethyl ascorbic acidSources: [45] [46]

Cruelty-free is a statement that the finished product and its ingredients have not been tested on animals. It does not say whether the formula contains animal-derived ingredients; that question is answered by the vegan statement. The basis for the statement is the brand's testing policy or a certification standard.

In the EU, animal testing has been banned for finished cosmetic products since 11 September 2004 and for ingredients since 11 March 2009; the sale in the EU of products and ingredients tested on animals has also been banned since 2009, and since 2013 for the remaining types of test.

Read in the guide →Related: Vegan cosmetics, DermocosmeticsSources: [47] [48] [49]

Dermocosmetics are a category of cosmetic products in which active ingredients with researched efficacy are formulated with a discipline grounded in dermatological knowledge, aiming to benefit the appearance of the skin without containing medicines that must be prescribed by a doctor; in the scientific literature they are also referred to as cosmeceuticals.

According to one review, the foundation of a cosmeceutical skincare routine is facial cleansing and moisturising; which of the claims made for new ingredients and technologies hold true should be examined separately. Dermocosmetic products also fall into the cosmetic product category and are not intended for medical treatment.

Related: Active concentration, INCI (ingredient list), Vegan cosmetics, Patch test (inner forearm)Sources: [50]

An emollient (softener) is a type of moisturising component that blends into the skin's top layer, making the surface feel smoother and softer. Moisturisers use emollients together with humectant and occlusive components.

It softens the look of dry, rough skin and helps the skin feel comfortable. One review counts the oils and humectants in moisturisers among their active components; the AAD also lists ingredients such as jojoba oil and shea butter among those to look for when choosing a cream for dry skin.

Read in the guide →Related: Humectant, TEWL (transepidermal water loss), Skin barrier, CeramideSources: [51] [52] [53]

INCI: Ethyl Ascorbic Acid

Ethyl ascorbic acid (Ethyl Ascorbic Acid) is an antioxidant ingredient: a derivative of ascorbic acid, the pure form of vitamin C, developed to improve its stability and its passage into the skin. Its percentage is not directly comparable with that of ascorbic acid.

It is used for antioxidant support and for radiance, dullness and the look of uneven tone. A laboratory study examined how this derivative is delivered into the skin in different solvent systems.

Read in the guide →Related: Vitamin C (ascorbic acid), Antioxidant, Niacinamide (vitamin B3), Active concentrationSources: [54] [55] [16]

Exfoliation is a skincare process that makes it easier for dead cells in the skin's top layer to come away; chemical exfoliation uses acids, while physical exfoliation uses rubbing or abrasive particles. Its intensity depends on the method, the strength of the product and how often it is used.

It helps reduce the look of dullness, rough texture and clogged pores linked to the build-up of dead cells on the surface. Chemical exfoliation uses AHAs, BHAs and PHAs; its degree depends on the type of acid, its concentration and the product's pH.

Read in the guide →Related: AHA (alpha hydroxy acids), BHA (beta hydroxy acids), PHA (polyhydroxy acids), Chemical peel, Skin barrierSources: [6] [24] [56]

INCI: Gentiana Lutea Root Extract

Gentian root extract is a plant extract obtained from the root of yellow gentian (Gentiana lutea) that contains gentiopicroside. It is used in eye-area formulas as a supporting ingredient with no declared concentration.

In one study, gentian extract containing gentiopicroside increased the expression of a gene linked to the antioxidant response in the laboratory; a small, placebo-controlled trial around the eyes reported a reduction in the look of redness in dark circles. The findings come from a single study and relate to the formula used in it.

Read in the guide →Related: Caffeine, Baobab extract, AntioxidantSources: [57]

INCI: Glycolic Acid

Glycolic acid is an exfoliating acid – the smallest molecule in the alpha hydroxy acid (AHA) family – that helps dead cells in the skin's top layer come away. Its effect is determined by concentration, pH and the rest of the formula, taken together.

Through exfoliation, it targets the look of rough texture, dullness, uneven tone and pores. Our sources contain no information that it changes pore size; the aim is a smoother-looking surface.

Read in the guide →Related: AHA (alpha hydroxy acids), Lactic acid, pH (skin and product pH), Exfoliation, Niacinamide (vitamin B3), Tasmanian pepper leaf extractSources: [6] [7] [58] [10]

A humectant is a type of moisturising component that draws water from the deeper layer of the skin up to its top layer. Hyaluronic acid, saccharide isomerate and gluconolactone are among the ingredients known in cosmetics for their humectant properties.

Moisturisers work with humectant, emollient and occlusive components: a humectant draws water to the skin's upper layers, an emollient blends into the top layer and softens the surface, and an occlusive covers the surface and slows water loss. The visible result is skin that feels more hydrated and plump.

Read in the guide →Related: Hyaluronic acid, Saccharide isomerate, Emollient, TEWL (transepidermal water loss), PHA (polyhydroxy acids)Sources: [51] [52] [59] [60]

INCI: Hyaluronic Acid, Sodium Hyaluronate, Hydrolyzed Hyaluronic Acid (formlar)

Hyaluronic acid is a glycosaminoglycan that also occurs in the body and attracts water; in cosmetics it is used as a humectant. It does not exfoliate the skin; its molecular weight determines how far it passes into the skin.

By holding moisture in the skin's upper layers, it supports a more hydrated, plumper look. In a Raman study, forms in the 20–300 kDa range passed through the skin's top layer, while forms in the 1000–1400 kDa range did not.

Read in the guide →Related: 8D hyaluronic acid, Humectant, Saccharide isomerate, Skin barrier, TEWL (transepidermal water loss)Sources: [1] [2] [61] [51]

A hybrid sunscreen, as defined by the AAD, is a type of sunscreen that combines one or more of the active ingredients found in chemical (organic) and physical (mineral) sunscreens.

According to the AAD, all sunscreens – chemical, physical or hybrid – form a protective layer on the skin that absorbs the sun's rays; physical filters also reflect them. Whether a product protects adequately is shown not by the type name but by the SPF, broad-spectrum and water-resistance criteria. These criteria are the AAD's general recommendation; the claims a sunscreen carries are shown on its label.

Read in the guide →Related: Mineral (physical) filter, Chemical (organic) filter, SPF (sun protection factor), Broad spectrum, PostbioticSources: [30] [62] [41]

INCI: Hydrolyzed Collagen

Hydrolysed collagen is a group of ingredients made up of low-molecular-weight peptides, obtained by breaking down the protein collagen with enzymes or in an acid or alkaline medium, and used in the food, drug and cosmetics industries.

According to one review, the properties of hydrolysed collagen depend on its source and production method; its traditional sources are cattle and pigs, and in recent years types obtained from marine organisms have also been researched. Collagen is among the ingredients added to cosmetic products such as creams.

Related: Peptide, Vegan cosmetics, INCI (ingredient list)Sources: [63] [64] [65]

INCI (International Nomenclature of Cosmetic Ingredients) is a naming system that ensures cosmetic ingredients are written with shared international names; it is used in the ingredient list on the pack. The same ingredient is written with the same name in every country.

Under EU cosmetics legislation, ingredients are generally listed in descending order of their weight at the time they are added to the product. The list shows the order; it does not show percentages, efficacy or the origin of the raw material. You can look up an ingredient's INCI name and function in the European Commission's CosIng database.

Read in the guide →Related: Active concentration, Preservative, 8D hyaluronic acid, Matrixyl™ 3000Sources: [49] [66]

INCI: Lactic Acid

Lactic acid is an alpha hydroxy acid (AHA) that helps dead cells shed from the skin's surface; it is a larger molecule than glycolic acid. Laboratory studies show that its effect depends on the acid's concentration and the product's pH.

Through exfoliation, it helps reduce the look of dullness, rough texture and uneven tone. The AAD also lists lactic acid among the ingredients to look for in creams and ointments recommended for dry skin.

Read in the guide →Related: AHA (alpha hydroxy acids), Glycolic acid, Chemical peel, pH (skin and product pH)Sources: [6] [8] [9] [53]

INCI: Glycyrrhiza Glabra Root Extract

Liquorice root extract is a plant extract obtained from the root of the liquorice plant (Glycyrrhiza glabra) and used in formulas as a supporting ingredient. Its main biologically active component is considered to be glycyrrhizic acid; its derivatives often appear in products for sensitive skin.

One review describes properties such as soothing and antioxidant effects for liquorice and its components. Our sources contain no strong human studies showing its effect on the skin; in s'hevec products, the main work on the look of uneven tone is done by the key actives.

Read in the guide →Related: Tranexamic acid, Alpha arbutin, Azelaic acid, Sensitive skinSources: [67] [11]

Matrixyl™ 3000 is the trade name of a peptide raw material used in creams for the look of firmness and fine lines; it appears in the ingredient list not under its own name but under the INCI names of the peptides it contains.

Creams containing peptides aim to support a firmer look and help with the look of fine lines; the evidence varies by peptide, and passage into the skin is the most important limitation. In Firm Baby Firm, it is used together with acetyl hexapeptide-8.

Read in the guide →Related: Peptide, Acetyl hexapeptide-8 (Argireline™), Baobab extract, INCI (ingredient list)Sources: [68] [69]

INCI: Titanium Dioxide, Zinc Oxide

A mineral (physical) filter is an inorganic UV filter, such as titanium dioxide or zinc oxide, that absorbs and also reflects UV rays in sunscreens. According to the AAD, a product whose only active ingredients are these is a physical sunscreen.

It contributes to protection against UVB and UVA. According to one review, when mineral filters are used in nanoparticle form to reduce the white, chalky look on the skin, they do not protect against visible light; for this purpose, tinted products use iron oxides and pigment-grade titanium dioxide.

Read in the guide →Related: Hybrid sunscreen, Chemical (organic) filter, Blue light (HEV), Zinc PCASources: [30] [31] [41]

Natural moisturising factor (NMF) is a mixture of small, water-soluble molecules formed inside the cells of the skin's top layer by the breakdown of the protein filaggrin; it contributes to the skin's ability to hold water.

How much water the top layer holds depends largely on the intercellular lipids and NMF. Its components include amino acids such as serine, glycine, alanine, histidine and arginine, as well as pyrrolidone carboxylic acid (PCA).

Read in the guide →Related: Sodium PCA, Skin barrier, TEWL (transepidermal water loss), pH (skin and product pH), CeramideSources: [70] [71] [40] [72]

INCI: Niacinamide

Niacinamide is the water-soluble amide form of vitamin B3, a versatile skincare ingredient that supports the look of balanced sebum and hydration and helps reduce the look of uneven tone. It does not exfoliate; it can be used both morning and evening.

Reviews describe effects on sebum balance and radiance that depend on concentration; one study examines its effect on the hydration and structure of the skin's top layer. This is why it often appears in formulas for the look of pores, shine, dark spots and red blotchiness.

Read in the guide →Related: Zinc PCA, Ethyl ascorbic acid, Tranexamic acid, Active concentration, Sebaceous filamentsSources: [73] [74] [75] [76]

Non-comedogenic is a label term stating that a product has been formulated so that it does not form pore plugs (comedones). According to one systematic review, this term on cosmetic packaging is not regulated by any regulatory body.

It is used as a pointer when choosing products for blemish-prone and oily skin; however, the test used to verify the term can vary from manufacturer to manufacturer. Methods that test the finished product on human skin give more meaningful information than inferences drawn from the ingredient list.

Read in the guide →Related: Comedogenic, Patch test (inner forearm), Sebaceous filamentsSources: [77] [43]

PA (Protection Grade of UVA) is a labelling system that shows a sunscreen's protection against UVA rays with plus signs, based on the test method of the Japan Cosmetic Industry Association (JCIA). The more plus signs, the higher the declared level of UVA protection.

The PA grade is based on the UVA protection factor (UVA-PF) measured by the persistent pigment darkening (PPD) method; this method has been shown to give reproducible results across different laboratories. The EU, for its part, recommends that the UVA protection factor be at least one third of the SPF.

Read in the guide →Related: UVA and UVB, SPF (sun protection factor), Broad spectrumSources: [78] [41] [79]

INCI: Panthenol

Panthenol is an ingredient called provitamin B5 because it is a precursor of vitamin B5; in skincare it is used to support hydration and barrier function. In studies it mostly appears under the name dexpanthenol; it is not an exfoliant.

In a placebo-controlled human study, formulas containing dexpanthenol increased hydration in the skin's top layer and reduced water loss through evaporation from the surface. In terms of appearance, it supports skin that feels more comfortable and hydrated.

Read in the guide →Related: Skin barrier, TEWL (transepidermal water loss), Humectant, AllantoinSources: [80] [81]

PAO (Period After Opening) is label information that shows how many months a cosmetic product can be used after it is first opened; it is written on the pack next to the open jar symbol as a number of months, such as 12M.

The expiry date applies to the unopened product; the PAO shows the period for the opened product. The period starts from first opening, not from the date of manufacture or purchase.

Read in the guide →Related: Preservative, INCI (ingredient list)Sources: [82] [83] [49]

A patch test (inner forearm) is a way of observing the skin's reaction by trying a new skincare product for a few days on a small area, such as the inner forearm, in the normal amount of use, before applying it to the face.

According to the AAD, trying a product on a small area first helps spot an adverse skin reaction in advance; some ingredients, such as preservatives, can cause allergic reactions.

Read in the guide →Related: Sensitive skin, Preservative, Chemical peelSources: [84] [24] [85]

A peptide is a molecule formed by a few amino acids linked in a short chain. Cosmetic reviews divide peptides into groups such as signal peptides, carrier peptides, peptides that affect nerve signalling and enzyme-inhibiting peptides.

Peptides are used in formulas that aim to help with the look of fine lines and support a firmer look; the evidence varies by peptide. One review notes that evidence of efficacy from human studies is often weak and that passage into the skin may be limited for reasons such as molecular size.

Read in the guide →Related: Acetyl hexapeptide-8 (Argireline™), Matrixyl™ 3000, Copper peptide (GHK-Cu), Hydrolysed collagenSources: [68] [65] [69]

pH is a scale that shows how acidic or basic a solution or surface is; the skin's surface is acidic. In acid skincare products, the product's pH determines the effect as much as the concentration does.

Some functions, such as barrier renewal and the skin's defence against microorganisms, are linked to the acidic nature of the skin's surface. According to the FDA, the degree of exfoliation in AHA products is determined by the product's pH as well as by the type and concentration of the acid.

Read in the guide →Related: AHA (alpha hydroxy acids), Glycolic acid, Skin barrier, Surfactant, Active concentrationSources: [72] [86] [58] [6]

INCI: Gluconolactone (glukonolakton), Lactobionic Acid (laktobionik asit)

PHAs (polyhydroxy acids) are a group of acids that, like AHAs, help dead cells come away from the surface, are less associated with sensory irritation and also have humectant properties. Gluconolactone and lactobionic acid are examples of this group.

According to one review, PHAs have a smoothing effect similar to that of AHAs, offer additional humectant properties and may support barrier function. In a study in which gluconolactone was applied, an increase in facial skin hydration was measured.

Read in the guide →Related: AHA (alpha hydroxy acids), Humectant, Exfoliation, Sensitive skinSources: [87] [60]

Photoageing is a process caused by the cumulative effect on the skin of long-term exposure to the sun's ultraviolet, visible and infrared rays, which makes the skin look older than its chronological age.

It shows up in signs such as wrinkles, uneven tone, changes in texture, loss of elasticity and visible capillaries; how severe the signs are depends on phototype: uneven tone is more prominent in darker skin, wrinkles in lighter skin. According to one review, it is largely preventable.

Read in the guide →Related: UVA and UVB, Antioxidant, SPF (sun protection factor), Blue light (HEV)Sources: [88] [18]

INCI: Lactobacillus Lysate (in the s'hevec product)

Postbiotics are a group of ingredients made up of metabolites produced by probiotic bacteria, used in skincare to support barrier function and the balance of the skin microbiota. On the label they may appear under names such as Lactobacillus Lysate.

According to one review, some research suggests that postbiotics may support barrier function and reduce the look of redness; the evidence in this area is still developing.

Read in the guide →Related: Skin barrier, Hybrid sunscreen, SPF (sun protection factor)Sources: [89]

INCI: Potassium Azeloyl Diglycinate

Potassium azeloyl diglycinate is a molecule derived from azelaic acid and used as a supporting ingredient in cosmetic formulas. Although its name refers to azelaic acid, it does not count as a substitute for it; the properties described for azelaic acid do not transfer to it directly.

In one human study, a cream containing this derivative was evaluated with measurements of the look of redness and of skin hydration; the researchers reported hydrating and soothing effects. The evidence is limited and cannot be read separately from the rest of the formula.

Read in the guide →Related: Azelaic acid, Zinc PCA, Niacinamide (vitamin B3)Sources: [90]

A preservative is an auxiliary substance in water-containing cosmetic formulas that keeps the growth of bacteria, mould and yeast under control, helping the product to be used safely throughout its period of use after opening. On the label it appears under separate INCI names.

Each time a product is opened, fingers and air carry in microorganisms; the preservative system keeps them under control. A study of cosmetics during use found contamination to be rare, but showed that the preservative system of some products could not adequately suppress microbial growth. Phenoxyethanol, Sodium Benzoate and Potassium Sorbate are preservatives often seen on labels.

Read in the guide →Related: PAO (period after opening), INCI (ingredient list), Patch test (inner forearm), Rice extractSources: [82] [83] [84] [77]

INCI: Oryza Sativa (Rice) Extract

Rice extract is a plant extract obtained from rice and used for radiance and hydration because of components such as phenolic compounds, betaine, squalene and tricin. On the label it appears as Oryza Sativa (Rice) Extract.

It is used to support radiance and moisture balance. A review of rice products shows that the evidence is mostly at the component level; in s'hevec products, rice extract is accompanied by niacinamide.

Read in the guide →Related: Niacinamide (vitamin B3), Tranexamic acid, Preservative, PHA (polyhydroxy acids)Sources: [91] [82] [83]

INCI: Saccharide Isomerate

Saccharide isomerate is a skin-conditioning ingredient derived from sugars – a humectant that draws water to the skin's upper layers – known under the trade name Pentavitin. On the label it appears as Saccharide Isomerate.

A 2025 report by the expert panel that assesses the safety of cosmetic ingredients describes it as a skin-conditioning humectant and finds it safe in cosmetics under current conditions of use and concentration. The visible result is skin that feels more hydrated and comfortable.

Read in the guide →Related: Humectant, Hyaluronic acid, 8D hyaluronic acidSources: [59] [92]

INCI: Salicylic Acid

Salicylic acid is an exfoliating acid, referred to in cosmetics as a BHA, that helps dissolve the plug of dead cells in the pore opening by loosening the bonds that hold cells together. It is chosen for the look of blackheads and pores.

It helps clear clogged pores; it targets the look of blackheads, clogged pores and rough texture. In a comparative study, unlike glycolic acid, it did not cause a significant increase in UV sensitivity; sun protection is still needed.

Read in the guide →Related: BHA (beta hydroxy acids), AHA (alpha hydroxy acids), Sebaceous filaments, Comedogenic, Zinc PCASources: [24] [25] [93] [26]

Sebaceous filaments are a normal structure made up of small dots – grey, yellowish or close to skin colour, similar to one another and arranged in rows – formed by sebum collecting in the pore opening, especially on and around the nose. They are assessed separately from blackheads.

Blackheads are dark and appear singly and irregularly, while sebaceous filaments are lighter in colour and more evenly spread. This distinction helps set realistic expectations for skincare.

Read in the guide →Related: Comedogenic, Salicylic acid, BHA (beta hydroxy acids), Zinc PCASources: [94] [44]

Sensitive skin is a condition defined by sensory reactions that people report themselves, such as tightness, stinging, burning, tingling or itching on the face; it can occur in every skin type – dry, oily, combination or normal.

According to one review, sensitivity can occur in normal skin, in skin with an impaired barrier or as part of certain skin conditions; many people report that their symptoms increase with environmental factors.

Read in the guide →Related: Patch test (inner forearm), Skin barrier, PHA (polyhydroxy acids), Centella asiatica (CICA)Sources: [95] [96] [11] [84]

The skin barrier is a protective structure that limits water loss, formed by the cells of the stratum corneum – the skin's top layer – and the layers of ceramides, cholesterol and free fatty acids that fill the spaces between them.

The barrier slows the escape of water and makes it harder for external substances to pass through. One review describes it as a four-layer structure – physical, chemical, microbiological and immunological; when it is weakened, tightness, flaking and stinging from familiar products can occur.

Read in the guide →Related: Ceramide, TEWL (transepidermal water loss), Natural moisturising factor (NMF), pH (skin and product pH), Sensitive skinSources: [51] [40] [70] [53]

INCI: Sodium PCA

Sodium PCA is the sodium salt of pyrrolidone carboxylic acid (PCA), one of the components of the skin's natural moisturising factor, used in cosmetic formulas to support moisture balance.

How much water the skin's top layer holds depends on natural moisturising factor together with the intercellular lipids; PCA is among the components of this mixture. In a formula, sodium PCA supports moisture balance together with ingredients such as glycerin and hyaluronic acid derivatives.

Read in the guide →Related: Natural moisturising factor (NMF), Zinc PCA, HumectantSources: [71] [70]

SPF (sun protection factor) is a value, determined by a standard test, that shows the protection a sunscreen provides against sunburn, that is, mainly against UVB rays. It does not on its own show UVA protection.

According to the AAD, SPF 15 filters 93% of UVB rays and SPF 30 filters 97%; no sunscreen filters them all. The FDA stresses that SPF describes protection relative to the amount of sun exposure, not how long you can stay in the sun.

Read in the guide →Related: UVA and UVB, Broad spectrum, PA (Protection Grade of UVA), UV index, Hybrid sunscreenSources: [30] [32] [62] [41]

A surfactant is a cleansing component in cleansers that emulsifies dirt, oil and microorganisms so that they can be rinsed away easily with water. Soaps are the oldest surfactants; synthetic cleansers combine different types of surfactant.

It clears the face of make-up, sunscreen and the dirt that builds up during the day. According to one review, soap causes the greatest change in the barrier and a rise in skin pH, while liquid facial cleansers affect the barrier less.

Read in the guide →Related: pH (skin and product pH), Skin barrier, PreservativeSources: [97] [98] [99] [52]

INCI: Tasmannia Lanceolata Leaf Extract

Tasmanian pepper leaf extract is a plant extract obtained from the leaves of Tasmannia lanceolata, a plant native to Australia whose leaves contain mainly polygodial. It is a supporting ingredient in s'hevec acid formulas.

In a cell study, a polyphenol-rich extract of Tasmanian pepper leaf suppressed certain inflammatory enzymes; a placebo-controlled trial with the leaf extract reported reduced roughness in the look of stretch marks. These findings do not transfer directly to its role in an acid formula.

Related: Glycolic acid, Salicylic acid, AHA (alpha hydroxy acids), BHA (beta hydroxy acids)Sources: [100] [101]

TEWL (transepidermal water loss) is the amount of water that evaporates per unit of time over a given area from the skin's top layer towards the surface; it is the most widely used objective measurement for assessing barrier function.

When TEWL rises, the barrier is thought to be struggling to hold water. Many studies have shown that moisturisers reduce TEWL; formulas containing dexpanthenol are also among the products studied with this measurement.

Read in the guide →Related: Skin barrier, Humectant, Emollient, Panthenol (provitamin B5)Sources: [102] [51] [81] [103]

INCI: Tocopherol

Tocopherol (vitamin E) is a fat-soluble vitamin that acts as an antioxidant by scavenging the free radicals that sunlight creates in the skin. In cosmetic formulas it appears as a skincare ingredient, and in moisturisers also as an auxiliary substance.

According to one review, vitamin E works as a free-radical scavenger against the harmful effects of the sun; experimental studies report photoprotective properties, but controlled human studies establishing dose and area of use are few. Vitamin C recycles vitamin E and works together with it.

Related: Antioxidant, Vitamin C (ascorbic acid), Emollient, PhotoageingSources: [17] [16] [52]

INCI: Tranexamic Acid

Tranexamic acid is a synthetic derivative of the amino acid lysine, used in skincare in formulas that target the look of dark spots and uneven tone. Although its name contains “acid”, it is not an exfoliant; it does not peel the skin.

One dermatology review reports that tranexamic acid can suppress melanin formation; in cosmetics, it is used to help reduce the look of dark spots, uneven tone and dark post-blemish marks. It is also known in medicine as a molecule used to reduce bleeding.

Read in the guide →Related: Alpha arbutin, Azelaic acid, Niacinamide (vitamin B3), PhotoageingSources: [104] [56]

The UV index is a scale developed by the World Health Organization and its partners that shows the level of ultraviolet radiation at a given place and on a given day as a number from zero upwards and indicates the need for protection.

The higher the value, the greater the potential for harm to the skin and eyes, and the sooner harm can occur. The reported value is the highest daily level reached during the four-hour period around solar noon.

Read in the guide →Related: SPF (sun protection factor), UVA and UVB, Broad spectrumSources: [105] [62] [6]

UVA and UVB are the two parts of the sun's ultraviolet rays that are tracked separately in skincare; as defined by the AAD, one is known as the ageing rays (UVA) and the other as the burning rays (UVB).

SPF mainly shows protection against UVB; UVA protection is assessed in the US with the term “broad spectrum” and in the EU by the ratio of the UVA protection factor to the SPF. According to one review, most broad-spectrum products in the US protect against short-wave UVA; few approved filters protect against long-wave UVA above 370 nm.

Read in the guide →Related: SPF (sun protection factor), PA (Protection Grade of UVA), Broad spectrum, Photoageing, Blue light (HEV)Sources: [30] [32] [18] [79]

Vegan cosmetics are cosmetic products whose formula contains no ingredients obtained from animals and no animal by-products. The label refers only to the source of the ingredients; on its own, it says nothing about how the product was tested.

An ingredient that does the same job can be obtained from a plant, synthetic or animal source; a vegan statement relies on checking the source of every raw material against supplier information. Vegan does not mean natural or organic.

Read in the guide →Related: Cruelty-free, INCI (ingredient list), Hydrolysed collagen, DermocosmeticsSources: [48] [106]

INCI: Ascorbic Acid

Vitamin C (ascorbic acid) is one of the well-known antioxidants in skincare and a vitamin used in formulas that target radiance, uneven tone and the cumulative effects of the sun. In its pure form it oxidises easily on contact with air.

One review reports that topical vitamin C is an antioxidant and decreases melanin formation; in cosmetics, it is used in formulas that aim to reduce the look of dullness and uneven tone. The same review notes that human studies are limited and that the main challenge is finding a stable formula that can pass into the skin.

Read in the guide →Related: Ethyl ascorbic acid, Antioxidant, Niacinamide (vitamin B3), PhotoageingSources: [16] [54]

INCI: Zinc PCA

Zinc PCA is a salt formed from zinc and PCA (pyrrolidone carboxylic acid), used in cosmetics in formulas for the look of sebum and shine. It is not the same as zinc oxide, the UV filter in sunscreens.

It appears in formulas for the look of pores and shine, mostly together with niacinamide. A review summarising the use of zinc in dermatology mentions antioxidant and immune-modulating properties; controlled research specific to zinc PCA, however, is limited.

Read in the guide →Related: Niacinamide (vitamin B3), Sodium PCA, Mineral (physical) filter, Sebaceous filamentsSources: [107] [108] [44]