medium

2-Bromo-2-Nitropropane-1,3-Diol (Bronopol)

Bronopol

A broad-spectrum preservative that releases formaldehyde and can act as a nitrosamine precursor.…

high

2-Hydroxyethyl Methacrylate (HEMA)

Hydroxyethyl Methacrylate

HEMA is the main reactive monomer in gel nail polish and dental adhesives, and the leading acryl…

medium

2-Mercaptobenzothiazole

A benzothiazole rubber accelerator and industrial biocide. A leading cause of shoe contact derma…

high

Acrylates & Methacrylates

Acrylates Copolymer

The family of reactive monomers (including HEMA) that make gel and acrylic nails set hard. A rap…

low

Adapalene

A third-generation synthetic retinoid for acne. Selective receptor binding makes it less irritat…

medium

Alcohol Denat

Denatured and short-chain alcohols that dissolve skin-barrier lipids, speed water loss and worse…

low

Alpha Arbutin

A bearberry-derived (now synthesised) tyrosinase inhibitor that fades hyperpigmentation gently.…

medium

Amyl Cinnamal (Amyl Cinnamaldehyde)

Amyl Cinnamal

A synthetic jasmine-like fragrance aldehyde and one of the eight Fragrance Mix I allergens. EU-l…

low

Argan Oil

Argania Spinosa Kernel Oil

A vitamin-E-rich plant oil from the Moroccan argan tree, balanced in oleic and linoleic acids. L…

low

Argireline (Acetyl Hexapeptide-8)

Acetyl Hexapeptide-8

A neuropeptide that mildly softens expression lines by partially interfering with the muscle-con…

low

Astaxanthin

A potent red carotenoid antioxidant from microalgae, active in both lipid and water environments…

low

Avobenzone

Butyl Methoxydibenzoylmethane

The most widely used UVA chemical filter worldwide. A low-frequency allergen with a strong safet…

low

Azelaic Acid

A dicarboxylic acid from grain that treats acne, fades hyperpigmentation, and calms rosacea. Nat…

high

Bacitracin

A polypeptide topical antibiotic in first-aid ointments. Consistently a top-5 contact allergen,…

low

Bakuchiol

A compound from the babchi plant (Psoralea corylifolia) that delivers retinol-like benefits for…

medium

Balsam of Peru

Myroxylon Pereirae

A natural resin used in fragrance and flavouring, and one of the most important "marker" allerge…

medium

Benzalkonium Chloride

A cationic antimicrobial used as a preservative/antiseptic. Both an irritant and a contact aller…

medium

Benzocaine

An ester-class local anaesthetic in lip, sunburn, throat, and hemorrhoid products. One of the mo…

low

Benzyl Salicylate

A sweet, floral-balsamic fragrance ester with mild UV-absorbing properties. A comparatively mild…

low

Benzylparaben

The least-used paraben preservative, and one banned in the EU as a precaution. A low-frequency c…

low

Betaine

A naturally derived osmolyte (trimethylglycine) that hydrates skin and reduces surfactant irrita…

medium

Budesonide

A common corticosteroid (creams, nasal sprays, inhalers) that can itself cause allergic contact…

low

Butylene Glycol

A small glycol used as a humectant, solvent, and slip agent in lightweight formulas. Very low al…

low

Butylparaben

A longer-chain paraben preservative. A low-frequency contact allergen like the rest of the famil…

medium

Carmine

A natural red pigment from cochineal insects, used in lipstick, blush and food. Mostly well tole…

low

Ceramides

Ceramide NP

Lipid molecules that make up much of the skin barrier. Replacing them topically restores hydrati…

low

Cetyl Alcohol

A waxy fatty alcohol used as an emollient, emulsifier, and thickener in most creams and conditio…

low

Cholesterol

A lipid that occurs naturally in skin and is essential to a healthy moisture barrier when applie…

high

Chromium (Potassium Dichromate)

Potassium Dichromate

A potent metal contact allergen. Hexavalent chromium in tanned leather and wet cement is the mai…

medium

Cinnamal (Cinnamaldehyde)

Cinnamal

A cinnamon-scented aldehyde and a comparatively potent EU-labelled fragrance allergen. Both an i…

medium

Cinnamic Alcohol (Cinnamyl Alcohol)

Cinnamyl Alcohol

A warm, balsamic fragrance alcohol from cinnamon, balsam of Peru, and hyacinth. A Fragrance Mix…

medium

Citral

A lemon-scented aldehyde abundant in lemongrass and citrus oils. A Fragrance Mix II allergen tha…

low

Citronellol

A naturally-occurring, rose-scented fragrance alcohol found in many essential oils and perfumes.…

medium

Cobalt Chloride

A contact allergen closely associated with nickel. In cosmetics it appears mostly as a trace pig…

medium

Cocamidopropyl Betaine (CAPB)

Cocamidopropyl Betaine

A coconut-derived amphoteric surfactant used in mild, sulfate-free cleansers. A genuine contact…

medium

Coconut Oil

Cocos Nucifera Oil

A highly occlusive plant oil that penetrates hair well but clogs facial pores for many people, a…

medium

Colophonium (Rosin)

Colophonium

A natural pine-tree resin used as a tackifier and film former. One of the most common contact al…

medium

Compositae Mix

A patch-test mixture screening for allergy to the Compositae (daisy/Asteraceae) family via its s…

low

Copper Peptides (GHK-Cu)

Copper Tripeptide-1

A naturally occurring peptide bound to copper that supports wound healing, collagen synthesis an…

low

Coenzyme Q10 (CoQ10 / Ubiquinone)

Ubiquinone

A naturally occurring antioxidant essential to cellular energy, replenished topically in anti-ag…

low

Cosmetic Dyes

Various

Synthetic FD&C and D&C colourants used across cosmetics and skincare. They add colour but no ski…

medium

Coumarin

A sweet, hay- and vanilla-like aromatic compound from tonka bean and other plants. A recognised…

low

Decyl Glucoside

A mild sugar-derived (alkyl polyglucoside) surfactant marketed as gentle and natural. Genuinely…

medium

Diazolidinyl Urea

A formaldehyde-releasing preservative (Germall II), stronger than imidazolidinyl urea. A consist…

medium

Dibucaine (Cinchocaine)

Dibucaine

A potent amide-class topical anaesthetic, mainly in hemorrhoid preparations. A recognised contac…

medium

Dimethylaminopropylamine (DMAPA)

Dimethylaminopropylamine

DMAPA is the residual manufacturing impurity in cocamidopropyl betaine (CAPB) that is the true a…

medium

Diphenylguanidine

A guanidine rubber vulcanisation accelerator in shoes, gloves, and sports gear. An increasingly…

medium

Disperse Blue 106

A blue disperse dye for synthetic fabrics (polyester, nylon, acetate) and one of the most common…

medium

Disperse Blue 124

An anthraquinone disperse dye for synthetic fabrics, closely related to Disperse Blue 106 and al…

medium

Disperse Yellow 3

An azo disperse dye for yellow/orange synthetic fabrics (and occasionally nail polish). An ACDS-…

medium

DMDM Hydantoin

A formaldehyde-releasing preservative used widely in shampoos and rinse-off products. Best known…

low

EGF (Epidermal Growth Factor)

sh-Oligopeptide-1

A growth-factor protein that signals skin cells to proliferate and regenerate, used in premium a…

high

Epoxy Resin

Bisphenol A Epoxy Resin

Bisphenol-A epoxy resin (DGEBA) is a widely used two-part adhesive, coating and craft material —…

medium

Essential Oils

Various

Essential oils are concentrated plant extracts — complex mixtures of sensitising fragrance chemi…

high

Ethyl Acrylate

A reactive acrylate monomer in acrylic nail systems and adhesives, and a strong skin sensitiser.…

medium

Ethylenediamine Dihydrochloride

Ethylenediamine

A stabiliser once common in topical creams, now largely removed — but a standard patch-test alle…

low

Ethylparaben

A short-chain paraben preservative, SCCS-approved as safe and among the least allergenic preserv…

medium

Eugenol

A clove-derived phenolic fragrance compound. A relatively potent EU-labelled fragrance allergen,…

medium

Farnesol

A floral sesquiterpene alcohol used both as fragrance and as a mild antibacterial in deodorants.…

low

Ferulic Acid

A plant-derived antioxidant that stabilises and amplifies vitamins C and E, boosting photoprotec…

high

Formaldehyde

A small, reactive molecule used as a preservative and in hair-straightening treatments. An IARC…

medium

Fragrance (Parfum)

Parfum

A mixture of fragrance chemicals. The most common cause of allergic contact dermatitis from cosm…

high

Fragrance Mix I

Parfum

A standardised patch-test mixture of 8 classic fragrance allergens. The most common positive in…

high

Fragrance Mix II

Parfum

A standardised patch-test mixture of 6 fragrance allergens not covered by Fragrance Mix I. Used…

low

Geraniol

A sweet, rose-like fragrance alcohol from rose, geranium, palmarosa, and citronella oils. A reco…

low

Gluconolactone (PHA)

Gluconolactone

A polyhydroxy acid (PHA) that exfoliates the surface as gently as possible while also hydrating…

high

Glutaraldehyde

A dialdehyde biocide used to sterilise medical instruments and to harden nails. Among the strong…

low

Glycerin

A plant-derived sugar alcohol that draws water into the skin. One of the safest, most-studied mo…

medium

Glycolic Acid

The smallest alpha hydroxy acid, from sugarcane. Loosens dead surface cells to brighten and smoo…

medium

Gold Sodium Thiosulfate

The standard patch-test agent for gold contact allergy — a surprisingly common metal allergy pre…

low

Granactive Retinoid (HPR)

Hydroxypinacolone Retinoate

Hydroxypinacolone retinoate (HPR), a retinoid ester that binds retinoid receptors directly witho…

medium

Hexyl Cinnamal

A synthetic jasmine/apple-scented fragrance aldehyde, very common in shampoos and soaps. An EU-l…

medium

Homosalate

A salicylate-family UVB chemical filter. Effective and cosmetically elegant, but under FDA absor…

low

Hyaluronic Acid

Sodium Hyaluronate

A naturally occurring sugar molecule (used as sodium hyaluronate) that draws water into the skin…

medium

Hydrocortisone-17-Butyrate

Hydrocortisone Butyrate

A moderately potent corticosteroid (brand Locoid). Despite its name it is a "labile ester" stero…

high

Hydroquinone

A potent tyrosinase inhibitor and the gold standard for melasma and stubborn pigmentation — with…

medium

Hydroxycitronellal

A synthetic floral (lily-of-the-valley/muguet) fragrance aldehyde and one of the eight Fragrance…

medium

Imidazolidinyl Urea

A formaldehyde-releasing preservative (Germall 115) used across lotions, shampoos, and makeup. A…

medium

Iodopropynyl Butylcarbamate (IPBC)

Iodopropynyl Butylcarbamate

An iodine-containing biocide preservative and an increasingly common contact allergen, particula…

medium

Isoeugenol

A clove/carnation-scented fragrance compound from clove and ylang-ylang oils. A Fragrance Mix I…

medium

Jasmine Absolute

Jasminum Officinale Oil

A complex natural fragrance from jasmine flowers containing 200+ compounds, several of them cont…

low

Jojoba Oil

Simmondsia Chinensis Seed Oil

A liquid wax ester from the jojoba plant that closely resembles human sebum. Low comedogenicity,…

medium

Kojic Acid

A fungal-fermentation byproduct that inhibits melanin production. Effective for hyperpigmentatio…

high

Bindi, Kumkum & Sindoor Allergens

Various

Traditional vermilion and forehead cosmetics (bindi, kumkum, sindoor) — often sold unlabelled —…

low

Lactic Acid

A larger, milder AHA that exfoliates while also acting as a humectant. Well tolerated; its effec…

low

Lanolin (Wool Wax)

Lanolin

A natural wax from sheep wool and one of the most effective barrier-repair emollients. Allergy i…

low

Lauryl Glucoside

A sugar-derived alkyl polyglucoside surfactant in natural shampoos and baby products. Mild for m…

low

Lavender Oil

Lavandula Angustifolia Oil

A popular essential oil that is a real contact allergen — mainly through air-oxidised linalool a…

medium

LHA (Capryloyl Salicylic Acid)

Capryloyl Salicylic Acid

A lipophilic salicylic-acid derivative that works inside pores like a BHA but more slowly and ev…

low

Licorice Root Extract

Glycyrrhiza Glabra Root Extract

A plant extract rich in glabridin and glycyrrhizin that inhibits melanin production and calms in…

low

Limonene

A citrus terpene present in most perfumed products. Weakly allergenic when fresh, but it oxidise…

low

Linalool

A floral terpene found in lavender, coriander, and hundreds of plants, present in the majority o…

high

Lyral (HICC)

Hydroxyisohexyl 3-Cyclohexene Carboxaldehyde

A potent synthetic muguet fragrance (HICC) that was one of Europe's most common fragrance allerg…

low

Magnesium Ascorbyl Phosphate

A water-soluble vitamin C derivative (MAP) that works at neutral pH without stinging and has a m…

low

Malic Acid

A mild AHA from apples and other fruits, used for gentle exfoliation and as a pH adjuster in mul…

low

Mandelic Acid

An almond-derived AHA whose large molecule penetrates slowly and evenly — the least irritating A…

low

Marula Oil

Sclerocarya Birrea Seed Oil

A vitamin-E-rich, high-oleic plant oil from the African marula tree. Oxidation-stable, low aller…

low

Matrixyl (Palmitoyl Pentapeptide-4)

Palmitoyl Pentapeptide-4

A signal peptide that stimulates collagen synthesis and softens fine lines, widely used in anti-…

high

Methylchloroisothiazolinone (MCI)

Methylchloroisothiazolinone

A chlorinated isothiazolinone preservative, almost always paired with methylisothiazolinone (MI)…

high

Methylisothiazolinone (MI)

Methylisothiazolinone

A potent synthetic preservative that became one of the leading causes of allergic contact dermat…

low

Methylparaben

A widely used paraben preservative. Despite a heavily negative public reputation, methylparaben…

low

Mexoryl SX (Ecamsule)

Terephthalylidene Dicamphor Sulfonic Acid

A water-soluble, photostable UVA (UVA2) filter patented by L'Oréal, used almost exclusively in i…

medium

Mixed Dialkyl Thioureas

A class of rubber accelerators used mainly in neoprene (not latex) — wetsuits, orthopaedic brace…

medium

Neomycin Sulfate

An aminoglycoside topical antibiotic in triple-antibiotic ointments, eye/ear drops, and some cre…

low

Niacinamide

A water-soluble form of vitamin B3 that brightens, hydrates, controls oil, calms redness, and su…

medium

Nickel Sulfate

The most prevalent contact allergen worldwide. In cosmetics it is mostly an indirect exposure —…

high

Oak Moss Absolute

Evernia Prunastri Extract

A natural lichen-derived perfume material and a Fragrance Mix I component. Its allergens atranol…

medium

Octinoxate

Ethylhexyl Methoxycinnamate

A widely used UVB chemical filter now declining in use. Banned in several reef zones, flagged fo…

low

Octisalate (Ethylhexyl Salicylate)

Ethylhexyl Salicylate

A salicylate-family UVB filter that also acts as a solvent for other UV filters. One of the gent…

low

Octocrylene

A chemical UV filter that absorbs UVB/short UVA, stabilises avobenzone, and adds water resistanc…

medium

Oleamidopropyl Dimethylamine

A conditioning surfactant structurally related to cocamidopropyl betaine. A contact allergen in…

medium

Oxybenzone (Benzophenone-3)

Benzophenone-3

A long-used chemical UV filter and the sunscreen ingredient most likely to cause photoallergic c…

high

p-tert-Butylphenol Formaldehyde Resin

An adhesive resin in leather shoes, watch straps and leather goods. Uniquely, it can cause not o…

low

Panthenol

A vitamin B5 precursor that hydrates, soothes irritation, and supports barrier repair and wound…

high

Parthenium (Whitetop Weed)

Parthenium Hysterophorus

An aggressively invasive Asteraceae weed (now across the Americas, Australia, Africa and Asia) t…

medium

Parthenolide

A sesquiterpene lactone and the main allergenic compound in feverfew (Tanacetum parthenium). A p…

medium

Peppermint Oil

Mentha Piperita Oil

A cooling essential oil rich in menthol and menthone. A common irritant and contact allergen for…

low

Phytosphingosine

A sphingoid base the skin uses to build its own ceramides, with gentle anti-inflammatory and ant…

high

Paraphenylenediamine (PPD)

p-Phenylenediamine

The primary permanent hair-dye chemical worldwide and a potent sensitiser. Reactions range from…

low

Pramoxine (Pramocaine)

Pramoxine

A morpholine-class topical anaesthetic for itch and minor pain. Neither ester nor amide, so it h…

medium

Propolis

A resinous substance bees make from plant resins and beeswax. A potent contact allergen rich in…

low

Propylene Glycol

A multitasking solvent, humectant, and penetration enhancer found in a huge share of cosmetics.…

low

Propylparaben

A paraben preservative commonly used alongside methylparaben for broad-spectrum protection. A lo…

high

Quaternium-15

A quaternary-ammonium preservative that releases more free formaldehyde than other common donors…

low

Resveratrol

A plant polyphenol (from grape skins / Japanese knotweed) with antioxidant and anti-inflammatory…

medium

Retinaldehyde (Retinal)

Retinal

A vitamin A derivative one enzymatic step from active retinoic acid — roughly 10x stronger than…

medium

Retinol

A vitamin A derivative (retinoid) that improves fine lines, pigmentation, acne, and texture. Cau…

low

Retinyl Palmitate

An ester of retinol and palmitic acid that converts slowly to active vitamin A. The mildest and…

low

Rosehip Oil

Rosa Canina Fruit Oil

A fast-absorbing oil from wild rose hips, high in linoleic acid, antioxidants, and trace vitamin…

medium

Salicylic Acid

A beta hydroxy acid that is oil-soluble, so it works inside the pore to clear sebum and dead cel…

medium

Sandalwood Oil

Santalum Album Oil

An essential oil from the sandalwood tree, prized in fine fragrance. Its α- and β-santalol compo…

low

Shellac

A natural resin from lac insects, used as a film-former in nail polish, hairspray and food glaze…

low

Sodium Laureth Sulfate (SLES)

Sodium Laureth Sulfate

A widely used foaming surfactant, milder than SLS but still capable of drying and irritating sen…

low

Sodium Lauryl Sulfate (SLS)

Sodium Lauryl Sulfate

A powerful, cheap surfactant used in cleansers and toothpaste. Causes dose-dependent irritation…

low

SNAP-8 (Acetyl Octapeptide-3)

Acetyl Octapeptide-3

An eight-amino-acid peptide developed as a more potent extension of Argireline, used in anti-wri…

low

Sodium Ascorbyl Phosphate

A water-soluble vitamin C derivative (SAP) that works at neutral pH without stinging. Gentle, st…

medium

Sodium Hydroxymethylglycinate

A glycine-derived, formaldehyde-releasing preservative often used in "natural"/clean products. T…

medium

Sodium Metabisulfite

A sulfite-family antioxidant and preservative used to stop oxidation (e.g. in vitamin C and brig…

low

Sodium PCA

The sodium salt of pyrrolidone carboxylic acid, a natural part of skin's moisturising factor. A…

low

Sorbitan Sesquioleate

A water-in-oil emulsifier in creams and medicated ointments. An occasional contact allergen that…

low

Squalane

A saturated, shelf-stable lipid (from olives or sugarcane) that mimics skin sebum and softens wi…

low

Succinic Acid

A small dicarboxylic acid (chemically a cousin of azelaic acid) with antibacterial, anti-inflamm…

low

Tartaric Acid

A mild AHA from grapes and other fruit, used for gentle exfoliation and as a pH adjuster in mult…

medium

Tea Tree Oil

Melaleuca Alternifolia Oil

An essential oil from the Australian tea tree, used for acne and dandruff. Genuinely antimicrobi…

medium

Tetracaine

A potent ester-class local anaesthetic used in ophthalmic drops and aesthetic numbing creams. Cr…

medium

Textile Dye Mix

A standardised patch-test mixture of disperse dyes used to diagnose clothing-related contact der…

low

Tetrahexyldecyl Ascorbate (THD Ascorbate)

Tetrahexyldecyl Ascorbate

An oil-soluble, highly stable vitamin C derivative that penetrates the skin's lipid layers, does…

high

Thiuram Mix

Tetramethylthiuram Disulfide

A mix of four thiuram rubber accelerators used to vulcanise gloves, elastic, and rubber goods. T…

low

Tinosorb M (Bisoctrizole)

Methylene Bis-Benzotriazolyl Tetramethylbutylphenol

A broad-spectrum UV filter (bisoctrizole) that works by both absorbing and physically scattering…

low

Tinosorb S (Bemotrizinol)

Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine

A next-generation chemical UV filter (bemotrizinol) with full-spectrum coverage, excellent photo…

low

Titanium Dioxide

A mineral UV filter covering UVB and short UVA, usually paired with zinc oxide for full broad-sp…

medium

Tixocortol-21-Pivalate

Tixocortol Pivalate

A hydrocortisone analogue used purely as a patch-test marker for "Group A" (hydrocortisone-type)…

medium

Tosylamide/Formaldehyde Resin in Nail Polish

Tosylamide/Formaldehyde Resin

A practical guide to the formaldehyde-based resin behind conventional nail polish — where it sit…

medium

Tosylamide Formaldehyde Resin

Tosylamide/Formaldehyde Resin

A leading cause of nail-polish allergic contact dermatitis whose signature is dermatitis far fro…

low

Tranexamic Acid

A lysine-derived compound, originally an anti-bleeding drug, now a well-tolerated topical (and p…

medium

Tretinoin

The active form of vitamin A, prescription-only and the most potent topical retinoid. Highly eff…

low

Urea

A natural component of skin's moisturising factor that hydrates at low concentrations and gently…

low

Uvinul A Plus (DHHB)

Diethylamino Hydroxybenzoyl Hexyl Benzoate

A modern UVA1 filter (DHHB) that matches avobenzone's deep-UVA coverage but stays stable in sunl…

low

Vitamin C (Ascorbic Acid)

Ascorbic Acid

The most-studied antioxidant in skincare; brightens, fades pigmentation, and supports collagen.…

low

Vitamin E (Tocopherol)

Tocopherol

A fat-soluble antioxidant that quenches free radicals, protects oils from going rancid, and cond…

medium

Zinc Dibutyldithiocarbamate

A zinc carbamate rubber accelerator in latex and neoprene goods — gloves, elastic, footwear. Cro…

medium

Zinc Diethyldithiocarbamate

A zinc dithiocarbamate rubber accelerator in latex products. Cross-reacts strongly with ZDBC and…

low

Zinc Oxide

A mineral (physical) UV filter giving broad-spectrum UVA+UVB protection. Photostable, reef-frien…