4-Methylbenzylidene Camphor (or Enzacamene or 4-MBC)

Cosmetics it’s found in: Sunscreen
What it’s used for: UV filter
Associated risks: Thyroid toxicity; hormone disruption

4-Methoxyphenol (MEHQ)

Cosmetics it’s found in: Nail polish; skin and body care; hair dye; sunscreen
What it’s used for: Antioxidant; stabilizer
Associated risks: Allergic reactions; skin sensitization; irritation of the eyes and respiratory tract

Acetaldehyde

Cosmetics it’s found in: Perfume
What it’s used for: Scent
Associated risks: Possible human carcinogen

Acrylamide

Cosmetics it’s found in: Skin and body care; hair care
What it’s used for: Producing polyacrylamide, a stabilizer and binder
Associated risks: DNA mutations; cancer; neurological, developmental, and male reproductive toxicity

Alcohol, Alcohol Denat, Ethanol, and SD Alcohol

Cosmetics it’s found in: Sunscreen; skin and body care; hair care; makeup; nail polish; perfume
What it’s used for: Preservative; antibacterial; anti-bacterial; deodorizing
Associated risks: Skin barrier disruption; irritation

Aluminum and Aluminum Compounds

Cosmetics it’s found in: Skin and body care; nail polish; sunscreen; makeup; hair care; perfume
What it’s used for: Color
Associated risks: Skin irritation; concerns about breast cancer and Alzheimer’s — probably safe under the legal threshold

Avobenzone (Butyl Methoxydibenzoylmethane)

Cosmetics it’s found in: Skin and body care; hair care; nail care; perfume
What it’s used for: UV filter
Associated risks: Endocrine disruption; toxic to aquatic ecosystems; allergic reactions

Benzalkonium Chloride

Cosmetics it’s found in: Skin and body care; hair care; makeup
What it’s used for: Preservative
Associated risks: Skin, eye, and respiratory irritation and allergic reactions; dry skin; dermatitis

Benzene

Cosmetics it’s found in: Not an ingredient, but trace amounts can be found in certain hand sanitizers, antiperspirants and sunscreens
Associated risks: Known human carcinogen; leukemia; blood disorders

Benzophenone (and Derivatives) 

Cosmetics it’s found in: Skin and body care; sunscreen; nail polish; hair care; makeup
What it’s used for: Protects products against UV light
Associated risks: Hormone disruption; eye and skin irritation; possible human carcinogen

Benzophenone-1
(Source)

Cosmetics it’s found in: Nail polish; skin and body care; hair care; makeup
What it’s used for: Protects products against UV light
Associated risks: Genotoxic potential; hormone disruption

Bisphenols (including Bisphenol A, or BPA)

Cosmetics it’s found in: Not an ingredient, but can leach from packaging
What it’s used for: Synthetizing plastic and resin
Associated risks: Potential toxicity to humans; hormone disruption

Butylated Hydroxyanisole (BHA — not to be confused with beta hydroxy acid)

Cosmetics it’s found in: Skin and body care; makeup; hair care
What it’s used for: Antioxidant, preservative and stabilizer
Associated risks: Skin irritation; hormone disruption; potential human carcinogen

Butylated Hydroxytoluene (BHT)

Cosmetics it’s found in: Skin and body care; hair care; makeup; perfume; nail polish
What it’s used for: Preservative
Associated risks: Skin and eye irritation; potential liver and kidney toxicity; potential thyroid issues

Butyloctyl Salicylate

Cosmetics it’s found in: Sunscreen
What it’s used for: Preventing skin irritation and increased sun sensitivity
Associated risks: Generally considered safe, but can be associated with reproductive and developmental toxicity

Camphor

Cosmetics it’s found in: Skin and body care; makeup; nail care
What it’s used for: Gives shine and prevents chipping in nail polish; fragrance; denaturant
Associated risks: Allergic reactions; toxicity

Carbon Black

Cosmetics it’s found in: Makeup; nail polish
What it’s used for: Pigment
Associated risks: Possible human carcinogen

Ceteareth (including Ceteareth-20)

Cosmetics it’s found in: Skin and body care; hair care; makeup
What it’s used for: Surfactant; emulsifying agent; solubilizing; cleansing agent
Associated risks: Potential contamination with 1,4-dioxane, a possible carcinogen and eye and skin irritant

Certain Fragrance Ingredients (Amyl cinnamal, Benzyl alcohol, Cinnamyl alcohol, Citral, Eugenol, Hydroxycitronellal, Isoeugenol, Amylcinnamyl alcohol, Benzyl salicylate, Cinnamal, Coumarin, Geraniol, Lyral, Anisyl alcohol, Benzyl cinnamate, Farnesol, Lilial, Linalool, Benzyl benzoate, Citronellol, Hexyl cinnamal, Limonene, Methyl 2-octynoate, Evernia prunastri extract [Oakmoss extract], Evernia furfuracea extract [Treemoss extract])

Cosmetics it’s found in: Sunscreen; skin and body care; makeup; perfume
What it’s used for: Scent
Associated risks: Allergic reactions; skin irritation

Chromium

Cosmetics it’s found in: Nail polish; skin and body care
What it’s used for: Pigment
Associated risks: Allergic reactions

Coal Tar Dyes (often listed as Cl followed by digits)

Cosmetics it’s found in: Skin and body care; hair care (including dyes)
What it’s used for: Colorant
Associated risks: Reproductive toxicity; may contain heavy metals; human carcinogen

Cocamide Diethanolamine (Cocamide DEA)

Cosmetics it’s found in: Skin and body care; hair care
What it’s used for: Foaming agent
Associated risks: Skin and eye irritation; potential toxicity; possible carcinogen

Colophonium
(Source)

Cosmetics it’s found in: Nail polish; makeup
What it’s used for: Binding; texturizing
Associated risks: Allergic reactions

Cyclopentasiloxane (Cyclomethicone)

Cosmetics it’s found in: Sunscreen; skin and body care; makeup
What it’s used for: Emollient
Associated risks: Generally safe for humans at authorized concentrations; environmental concerns; hormone disruption; animal carcinogen at high concentrations

Dibutyl Phthalte (DBP)

Cosmetics it’s found in: Nail polish
What it’s used for: Plasticizer
Associated risks: Endocrine disruption; reproductive dysfunction; developmental issues

E-Series Glycol Ethers

Cosmetics it’s found in: Sunscreen; other cosmetics
What it’s used for: Solvent
Associated risks: Neurological, hepatic, hematological, endocrine, reproductive, and other toxic effects

Ethanolamine
(Source)

Cosmetics it’s found in: Hair care; skin and body care; makeup 
What it’s used for: pH adjuster
Associated risks: Skin and eye irritation; allergic reactions; potential carcinogenic effects

Ethyl Tosylamide

Cosmetics it’s found in: Nail polish
What it’s used for: Plasticizer; film former
Associated risks: Strong allergic reactions; potential builder of antibiotic resistance; banned for use in cosmetics in Europe

Formaldehyde, Formaldehyde Resin, and Formaldehyde Releasers (Diazolidinyl Urea, Imidazolidinyl Urea, DMDM Hydantoin, Quaternium 15, Methenamine, Polyoxymethylene Urea, Sodium Hydroxymethylglycinate, Methylene Glycol and more)

Cosmetics it’s found in: Makeup; hair care; skin and body care; sunscreen; nail polish
What it’s used for: Preservative
Associated risks: Human carcinogen; allergic contact dermatitis

Fragrance

Cosmetics it’s found in: Skin and body care; perfume; hair care; sunscreen; nail polish
What it’s used for: Scent
Associated risks: Allergic reactions; dermatitis; respiratory distress; potential adverse effects on the reproductive system; undisclosed ingredients

HEMA

Cosmetics it’s found in: Nail enhancements
What it’s used for: Building or lengthening the nail
Associated risks: Allergic reactions

Homosalate

Cosmetics it’s found in: Sunscreen
What it’s used for: UV light absorber
Associated risks: Hormone disruption; may stimulate the growth of breast cancer cells; toxic to marine life and reefs

Hydroquinone

Cosmetics it’s found in: Skin lightening products; some makeup as a dark spot corrector
What it’s used for: Skin-bleaching
Associated risks: Allergic reactions; contact dermatitis; hives; ochronosis

Isothializones 

Cosmetics it’s found in: Hair care; skin and body care
What it’s used for: Preservative
Associated risks: Allergic reactions; skin sensitivity; potential neurotoxicity

Lead and Lead Acetate 

Cosmetics it’s found in: Makeup
What it’s used for: Not an ingredient, a contaminant
Associated risks: Neurotoxicity; hormone disruption; reproductive toxicity; in high amounts, may lead to learning disabilities and acute  neurologic and psychologic dysfunction; skin and eye irritation

Lilial (Lily Aldehyde, or Butylphenyl Methylpropional)

Cosmetics it’s found in: Hair care; skin and body care; perfume
What it’s used for: Scent
Associated risks: Reproductive toxicity; allergic reactions

Mercury

Cosmetics it’s found in: Not an ingredient, a contaminant
Associated risks: Allergic reactions; skin irritation; kidney damage; nervous system disorders; toxic to the developing brain during pregnancy, infancy and childhood

Methacrylate Monomers (including Methyl Methacrylate)

Cosmetics it’s found in: Artificial nail and lash products
What it’s used for: Adhesive
Associated risks: Skin, eye, and respiratory irritation; contact dermatitis

Methyl Ethyl Ketone (MEK)

Cosmetics it’s found in: Nail polish and nail care
What it’s used for: Solvent
Associated risks: Skin irritation; lung irritation; nervous system disruption; allergic reactions; hormone disruption

Methylisothiazolinone

Cosmetics it’s found in: Hair care; skin and body care; sunscreen; makeup
What it’s used for: Preservative
Associated risks: Allergic reactions; potentially neurotoxic

Methylene Chloride (Dichloromethane)
(Source)

Cosmetics it’s found in: Makeup; gel nail polish remover; hair spray
What it’s used for: Solvent
Associated risks: Probable human carcinogen; banned by the FDA

Mineral Oil (if poorly processed; highly purified is considered safe)
(Source)

Cosmetics it’s found in: Skin and body care; makeup; hair care
What it’s used for: Emollient
Associated risks: Genotoxic; carcinogen

Musk Ketone

Cosmetics it’s found in: Perfume
What it’s used for: Scent
Associated risks: Environmental concerns; can persist in body fat and breast milk; being investigated for its possible role in increasing cancer risk

Nanoparticles (of Zinc Oxide and Titanium Dioxide)

Cosmetics it’s found in: Sunscreen
What it’s used for: Sun protection
Associated risks: Safe when used topically; when inhaled or ingested can impact lung health; potential environmental impact

Nonoxynols (or Nonylphenol Ethoxylates, or Nonylphenol) 

Cosmetics it’s found in: Skin and body care; hair care; perfume
What it’s used for: Emulsifier; foaming agent; solubilizing agent; wetting agent
Associated risks: Hormone disruption; risks to aquatic ecosystems

Octinoxate (Ethylhexyl Methoxycinnamate)

Cosmetics it’s found in: Sunscreen; skin and body care; perfume; hair care; makeup
What it’s used for: UV filter
Associated risks: Potential hormone disruption (including delayed puberty); negative impact on aquatic ecosystems and coral reefs

Octocrylene

Cosmetics it’s found in: Sunscreen; nail polish; hair care; makeup; skin and body care
What it’s used for: UV absorber
Associated risks: Potential hormone disruption; allergic reactions; harmful to marine ecosystems

Oxybenzone
(Source)

Cosmetics it’s found in: Sunscreen; skin and body care; hair care; perfume; nail polish; makeup
What it’s used for: UV filter
Associated risks: Possible hormone disruption; allergic reactions; eye and skin irritation; harmful to marine ecosystems

P-Phenylenediamine (PPD) 

Cosmetics it’s found in: Hair dyes
What it’s used for: Hair colorant
Associated risks: Severe allergic reactions; skin and eye irritation; strict regulations are in place

Parabens (on a label, look for the suffix “paraben” as in ethylparaben or butylparaben)

Cosmetics it’s found in: Hair care; skin and body care
What it’s used for: Preservatives
Associated risks: Hormone disruption; reproductive toxicity

Petrolatum (safe if highly refined)
(Source)

Cosmetics it’s found in: Hair care; skin and body care; makeup
What it’s used for: Moisturizing agent
Associated risks: Potential contamination with PAHs (polycyclic aromatic hydrocarbons), a possible carcinogen

Petroleum Distillates (may be listed as Paraffinum Liquidum, Petrolatum, Mineral Oil, Liquid Paraffin)

Cosmetics it’s found in: Makeup; soap
What it’s used for: Moisturizer; solvent
Associated risks: May increase cancer risk; skin irritation

PFAS (per- and polyfluoroalkyl substances, including PFCs)

Cosmetics it’s found in: Makeup; nail polish; skin and body care
What it’s used for: Conditioner; texturizer
Associated risks: Forever chemicals; long-term ecological concerns; increased risk of cancer; hormone disruption; liver damage; immune system damage

PEGs (polyethylene glycol derivatives — safe if adequately purified)

Cosmetics it’s found in: Hair care; makeup; skin and body care
What it’s used for: Surfactant; emulsifier; cleansing agent; humectant; skin conditioner
Associated risks: May release small amounts of 1,4-dioxane, a potential carcinogen and eye and skin irritant; may increase skin permeability and vulnerability to toxins

Phthalates (including Dibutyl Phthalate [DBP], Diethyl Phthalate [DEP], and Dimethyl Phthalate [DMP])
(Source)

Cosmetics it’s found in: Nail polish; in various products under the label “fragrance”
What it’s used for: Scent; plasticizer
Associated risks: Hormone disruption; reproductive and developmental risks

Polyethylene Glycol (safe when adequately purified)
(Source)

Cosmetics it’s found in: Hair care; makeup; skin and body care
What it’s used for: Emulsifier; surfactant; conditioner
Associated risks: May release trace amounts of 1,4-dioxane, an eye, skin and respiratory irritant

Propylene Glycol
(Source)

Cosmetics it’s found in: Skin and body care; hair care; perfume; makeup; nail polish; sunscreen
What it’s used for: Humectant; scent; texturizer; skin conditioner
Associated risks: Irritant; allergic reactions in some people (but well tolerated by many); allergic contact dermatitis; contact urticaria

Quaternary Ammonium Compounds (QAC)

Cosmetics it’s found in: Hair care; skin and body care; makeup
What it’s used for: Antimicrobial; disinfectant; sanitizer; surfactant
Associated risks: Hair buildup; skin irritation, sensitization and dermatitis; respiratory and immune issues; reproductive and developmental toxicity; ecotoxicity

Resorcinol
(Source, Source)

Cosmetics it’s found in: Hair care; skin and body care
What it’s used for: Hair colorant; disinfectant; antiseptic; surfactant
Associated risks: Endocrine disruption; thyroid issues; immune system toxicity; allergic reactions; skin irritation

Retinyl Palmitate
(Source)

Cosmetics it’s found in: Sunscreen; skin and body care; makeup; hair care; nail polish
What it’s used for: Improve texture of skin and hair
Associated risks: Typically considered safe, however caution is advised during pregnancy; may accelerate the development of tumors on sun-damaged skin; may contribute to DNA damage; potential photocarcinogenicity in animals

Selenium Sulfide
(Source)

Cosmetics it’s found in: Hair care
What it’s used for: Treats infections; reduces flaking and itching
Associated risks: Allergic reactions; suspected carcinogen

Silica (Silicon Dioxide)

Cosmetics it’s found in: Skin and body care; makeup; hair care; perfume; nail polish
What it’s used for: Absorbent; anti-caking agent; bulking agent; opacifying agent
Associated risks: May be carcinogenic if inhaled

Silicone
(Source)

Cosmetics it’s found in: Hair care; makeup; skin and body care; sunscreen
What it’s used for: Texturizer; hydrator; barrier forming
Associated risks: No health risks; may cause hair build-up, greasiness, dryness and brittleness

Siloxanes

Cosmetics it’s found in: Sunscreen; hair care; skin and body care
What it’s used for: Texturizer
Associated risks: Environmental concerns; hormone disruption; fertility concerns; linked to tumors in animals

SLS or SLES (or Sulfates)

Cosmetics it’s found in: Skin and body care; hair care; makeup
What it’s used for: Surfactant; foaming agent
Associated risks: Skin and eye irritation; may form 1,4-dioxane, a possible carcinogen; harmful to aquatic ecosystems

Styrene and Styrene Acrylates Copolymer

Cosmetics it’s found in: Nail polish; hair care; skin and body care; sunscreen
What it’s used for: Colorant
Associated risks: Allergic reactions; hormone disruptions; potential carcinogen; associated with neurotoxicity

Synthetic Musk

Cosmetics it’s found in: Perfume; skin and body care
What it’s used for: Scent
Associated risks: Environmental concerns; may persist in body fat and breast milk; allergic reactions; eye, nose and throat irritant; hormone disruption

Talc
(Source)

Cosmetics it’s found in: Makeup; nail polish; skin and body care
What it’s used for: Anti-caking agent; absorbent; opacifying agent; texturizer
Associated risks: May contain traces of asbestos if not adequately purified — asbestos is associated with respiratory toxicity and cancer; even asbestos-free talc may be toxic and carcinogenic

Teflon (or PTFE)

Cosmetics it’s found in: Makeup; skin and body care
What it’s used for: Bulking agent; texturizer
Associated risks: Environmental concerns; health concerns; potential carcinogen

Tert-Butyl Hydroperoxide

Cosmetics it’s found in: Nail systems
Associated risks: Skin and eye irritant; may cause skin burns

Titanium Dioxide
(Source)

Cosmetics it’s found in: Sunscreen; skin and body care; hair care; nail polish; makeup
What it’s used for: UV filter; whitening agent
Associated risks: Considered safe for dermal application, but classified as a possible carcinogen

Toluene

Cosmetics it’s found in: Fake lashes; hair dyes; nail products
What it’s used for: Adhesive; finishing agent
Associated risks: Neurotoxicant; irritant; breathing issues; headaches; nausea; immunotoxicity; may impair fetal development

Toluene 2,5 Diamine 

Cosmetics it’s found in: Hair care
What it’s used for: Colorant
Associated risks: Allergic reactions

Triclosan

Cosmetics it’s found in: Antibacterial soaps; skin and body care; makeup
What it’s used for: Antimicrobial
Associated risks: Hormone disruption; contact dermatitis; skin irritation; can contribute to antibiotic resistance

Triphenyl Phosphate (TPHP)

Cosmetics it’s found in: Nail polish
What it’s used for: Flame retardant; plasticizer
Associated risks: Hormone disruption

Xylene

Cosmetics it’s found in: Nail care
What it’s used for: Solvent
Associated risks: Eye, nose, skin and throat irritant; may harm fetuses; headache; dizziness; confusion; long-term exposure may effect liver and kidneys

Zinc Oxide

Cosmetics it’s found in: Sunscreen; makeup; skin and body care; hair care
What it’s used for: UV filter
Associated risks: Considered safe as a cream; can cause lung irritation in spray form