Index / Ingredient dossiers
What the actives actually do
44 ingredient dossiers and growing. Effective concentrations, pH requirements, mechanism of action — every claim sourced to the primary literature.
Antioxidants & vitamin C 4
Daytime free-radical defense and glow — best worn under SPF.
- Ferulic Acid Ferulic acid is a plant-derived phenolic antioxidant that scavenges reactive oxygen species via its phenolic hydroxyl group, absorbs UV ligh… Effective: 0.5-1% (leave-on); 12-14% (peels)
- L-Ascorbic Acid (Vitamin C) L-ascorbic acid is a water-soluble antioxidant that neutralises reactive oxygen species generated by UV radiation and environmental stressor… Effective: 8-20%
- Tocopherol (Vitamin E) Alpha-tocopherol is the primary lipid-soluble chain-breaking antioxidant in the human stratum corneum, delivered to the skin surface via seb… Effective: 1% (studied combination); 0.00000001-36% (CIR documented range)
- Vitamin C Derivatives Pure vitamin C — L-ascorbic acid — is the gold standard with the deepest evidence, but it has two real-world problems: it oxidizes quickly (… Effective: Varies by derivative — SAP & MAP are documented in cosmetics up to ~3% (SAP studied at 5% for acne); ethyl ascorbic acid and ascorbyl glucoside commonly ~2%; THD across a wide range — so the % only means something once you know which derivative
Brightening & dark spots 6
Gentle pigment-and-tone actives. Start with the brightening decision guide. See the guide →
- Alpha-Arbutin Alpha-arbutin is a biosynthetic glycosylated hydroquinone derivative — specifically, 4-hydroxyphenyl alpha-D-glucopyranoside — in which a gl… Effective: 1–2%
- Azelaic Acid Azelaic acid is a naturally occurring straight-chain C9 dicarboxylic acid (found in wheat, rye, and barley) with four distinct pharmacologic… Effective: 10-20%
- Kojic Acid Kojic acid is a naturally occurring fungal metabolite produced during fermentation by Aspergillus and Penicillium species (notably in koji —… Effective: 1-2%
- Licorice Root (Glycyrrhiza Glabra) Licorice root is one of skincare's favourite 'gentle brighteners', but the honest version of the story is that 'licorice' is really two diff… Effective: No standardized cosmetic concentration — and the marker compound (glabridin or licochalcone A) and species matter far more than a generic 'licorice extract' percentage
- Niacinamide (Vitamin B3) Niacinamide is the amide form of vitamin B3 (nicotinic acid). Effective: 2–5%
- Tranexamic Acid Tranexamic acid is a synthetic lysine analog originally developed as an oral antifibrinolytic drug to control bleeding. Effective: 2-5%
Retinoids & firming 6
The strongest evidence for lines and texture — used at night.
- Adapalene Adapalene is the single most important acne ingredient you can buy without a prescription: it's a genuine, prescription-strength retinoid th… Effective: 0.1% (the OTC strength, Differin) and 0.3% (prescription, for moderate-to-severe acne); also in once-daily fixed-dose combinations with benzoyl peroxide 2.5%
- Bakuchiol Bakuchiol is a meroterpene phenol isolated from the seeds of Psoralea corylifolia (babchi plant). Effective: 0.5-2%
- Copper Peptides (GHK-Cu) Copper peptides — almost always GHK-Cu (copper tripeptide-1) — are one of the more scientifically interesting 'regenerative' actives in skin… Effective: Used at low levels in serums (commonly around 1% of the copper-peptide complex); studies show its tissue-building effect is concentration-dependent, but high cosmetic percentages aren't necessarily better, and the optimal facial dose isn't well established
- Peptides Cosmetic peptides are short chains of amino acids — typically two to ten residues — used in skincare to signal, carry, or inhibit. Effective: varies by peptide; typically 0.0003–2% (3–200 ppm) for signal and carrier peptides; up to 10% for argireline in clinical studies
- Retinaldehyde (Retinal) Retinaldehyde (retinal) is the vitamin A aldehyde that sits exactly one oxidative step away from retinoic acid in the skin's retinoid conver… Effective: 0.05–0.1%
- Retinol (Vitamin A) Retinol is the cosmetically available form of vitamin A. Effective: 0.1-1%
Exfoliants & acne actives 6
Acids and anti-acne actives that resurface and clear — pace them carefully.
- Benzoyl Peroxide Benzoyl peroxide is an organic peroxide and potent bactericidal agent used as an over-the-counter (OTC) drug active ingredient for acne vulg… Effective: 2.5-10%
- Glycolic Acid (AHA) Glycolic acid is the smallest-molecule alpha-hydroxy acid (AHA; MW 76 Da), derived from sugar cane. Effective: 4-10% (OTC cosmetic leave-on); 20-70% (professional peels)
- Lactic Acid Lactic acid is an alpha-hydroxy acid (AHA; MW 90 Da; pKa 3.86) with a dual mechanism: it accelerates corneocyte desquamation by disrupting c… Effective: 5-12% (consumer leave-on); up to 30-70% (professional peels)
- Mandelic Acid (AHA) Mandelic acid is an alpha-hydroxy acid (AHA) derived from the hydrolysis of amygdalin found in bitter almonds. Effective: 5-10% (OTC leave-on); up to 45% (professional chemical peels)
- Polyhydroxy Acids (PHA) Polyhydroxy acids are the gentle, sensitive-skin generation of exfoliating acids. Effective: Used as leave-on serums/toners (commonly a few to ~10%) and as in-office or at-home peels (gluconolactone studied at 10–30%); the gentle profile means useful strengths with less irritation
- Salicylic Acid (BHA) Salicylic acid is a lipophilic (oil-soluble) beta-hydroxy acid (BHA) that works via three converging mechanisms: it is keratolytic — dissolv… Effective: 0.5-2% (OTC acne); up to 30% (professional peels)
Barrier & hydration 11
The supportive layer: moisture, soothing, and barrier repair.
- Avobenzone Avobenzone is the chemical-sunscreen answer to the question the mineral filters also solve: how do you protect against long UVA? Effective: Up to 3% in US over-the-counter sunscreens (the regulatory maximum) — but the number matters far less than whether the formula is photostabilized; avobenzone is included despite its instability because there are so few UVA alternatives
- Beta-Glucan Beta-glucan is a polysaccharide — a chain of glucose units — found in the cell walls of yeast, fungi (mushrooms), and bacteria, and in cerea… Effective: No standardized cosmetic concentration — and source/structure matter more than the percentage. Oat, yeast, and mushroom β-glucans differ enough that a label percentage tells you little on its own
- Ceramides Ceramides are a family of sphingolipids that make up roughly 40–50% of the stratum corneum lipid matrix by weight. Effective: 0.001–1%
- Ectoin Ectoine is one of skincare's quiet overachievers: an ingredient with a genuinely unusual amount of controlled human evidence behind a simple… Effective: Clinical eczema creams use roughly 5.5–7% ectoine; cosmetic serums and moisturizers often use less and rarely disclose the exact percentage, so judge a product on its evidence and feel rather than a number
- Glycerin Glycerin (glycerol) is the quiet workhorse of skincare — the gold-standard humectant that draws water into the upper layers of skin and help… Effective: Effective at low levels — commonly a few percent in moisturizers, more in dedicated humectant serums; you don't need a high dose to benefit
- Hyaluronic Acid Hyaluronic acid (HA) is a naturally occurring, non-sulfated glycosaminoglycan found in the extracellular matrix of connective tissue, synovi… Effective: 0.1-2%
- Panthenol (Provitamin B5) Panthenol is provitamin B5 — the skin converts it to pantothenic acid (vitamin B5), a building block of coenzyme A, which the body needs to … Effective: Commonly used around 1–5% (e.g. 5% in well-known barrier balms); the controlled studies tested finished panthenol/dexpanthenol emollients rather than a single isolated percentage
- Squalane Squalane is one of skincare's best 'boring in a good way' ingredients — a lightweight oil that your skin already recognizes. Effective: No 'active %' — squalane is an emollient/oil, used anywhere from a few percent in a formula up to 100% as a pure facial oil
- Titanium Dioxide Titanium dioxide is the other mineral sunscreen filter — zinc oxide's constant partner. Effective: Used in sunscreens up to about 25% (the practical maximum), usually as micronized/nano coated particles to reduce the white cast — and very often combined with zinc oxide rather than used alone
- Urea (Carbamide) Urea is one of dermatology's quiet heavyweights — and the single most important thing to understand about it is that what it does depends en… Effective: Concentration IS the function: roughly 2–10% = humectant/hydrating; ~15–30% = keratolytic (smooths rough, thickened skin); up to ~40% for hard callus, heels and nails
- Zinc Oxide Zinc oxide is the workhorse mineral sunscreen — an inorganic UV filter that the rest of this site keeps pointing you toward every time it sa… Effective: Used in sunscreens up to about 25% (the practical US maximum), typically as micronized/nano particles to reduce the white cast; the % interacts with SPF and feel rather than being a single 'effective dose'
Soothing botanicals & K-beauty 11
Calming, antioxidant plant actives and fermented essences.
- Allantoin Allantoin is the ingredient you've used a hundred times without noticing it. Effective: Typically used at low levels as a supporting soother — the cosmetic review documents use up to 2%; research soothing/wound formulas have gone higher (e.g. 5% in a wound-healing emulsion)
- Centella Asiatica (Cica) Centella asiatica is a tropical herb whose biological activity in skin is attributed primarily to four pentacyclic triterpene compounds: asi… Effective: 0.1–5% whole extract; TECA standardized to a defined ratio of four triterpenes; topical studies typically use ~0.5–5% extract
- Ferment Filtrates (Galactomyces, Bifida, Saccharomyces) Ferment filtrates are compositionally undefined mixtures produced by culturing yeast or bacteria — most commonly Galactomyces genus fungi, B… Effective: Not meaningfully defined — often 90%+ in essence products
- Green Tea (Camellia Sinensis) Green tea (Camellia sinensis) leaf extract is one of skincare's best-loved botanicals, and its appeal is real — it's rich in catechin polyph… Effective: No single standardized percentage — what matters is the catechin/EGCG content and, above all, whether that EGCG is still intact in the bottle
- Heartleaf (Houttuynia Cordata) Heartleaf — Houttuynia cordata, a herb long used in East Asian traditional medicine and nicknamed the 'Chinese herbal antibiotic' — is the K… Effective: No standardized cosmetic concentration. Korean 'heartleaf 77%/X%' labels describe how much of the formula is the extract, not a standardized level of any active compound
- Madecassoside Madecassoside is the headline molecule behind the whole 'cica' trend. Effective: No established 'effective %' for isolated topical madecassoside — it's typically delivered as part of a standardized Centella asiatica extract or a centella/TECA blend, and the extract's standardization (how much madecassoside it actually contains) matters more than any single number on the label
- Mugwort (Artemisia) Mugwort — botanically Artemisia, a genus of around 500 species in the daisy (Asteraceae/Compositae) family — is the K-beauty 'calming' herb … Effective: No standardized cosmetic concentration — and which Artemisia species (plus the harvest season) matters more than the percentage. Korean 'mugwort X%' labels describe extract content, not a standardized active level
- Polynucleotides / PDRN ("Salmon DNA") Polynucleotides (PN) and polydeoxyribonucleotides (PDRN) are DNA-derived biopolymers — chains of deoxyribonucleotide fragments, traditionall… Effective: No established topical concentration. The clinical evidence is for injected polynucleotide fillers/'skin boosters' dosed by a practitioner (e.g. ~0.05 mL across many intradermal points per session), not a labelled cream percentage
- Propolis (Bee Propolis) Propolis is a resinous material honeybees make by combining plant and tree resins with their own secretions and wax — a kind of structural '… Effective: No standardized cosmetic concentration. The clinical wound-healing RCT used a 5% propolis ointment; cosmetic 'propolis extract' is rarely quantified and its activity depends on type/origin more than on a single percentage
- Rice (Oryza Sativa) Rice (Oryza sativa) is the foundation of a huge wave of 'glow' toners, essences and serums, and its appeal is real but easy to overstate. Effective: No standardized cosmetic concentration — and the rice FORM and variety matter more than the percentage. 'Rice water 70%' or 'rice extract' on a label describes content, not a standardized active dose
- Snail Mucin (Snail Secretion Filtrate) Snail mucin (INCI: snail secretion filtrate, SSF) is the filtered mucus secreted by land snails — most commonly Helix aspersa Müller in Kore… Effective: Clinical SCA studies used ~8% (cream) to 40% (serum); Korean SSF essences are often labelled 92–97% filtrate, but that is filtrate content, not standardized active content