What is in nail polish, ingredient by ingredient

A bottle of nail polish contains five kinds of ingredient with five separate jobs. One forms the film, one keeps that film bendy, one makes it grip and gloss, one dissolves everything so it can be brushed on, and one gives the colour. Everything else in the ingredient list is there to keep those five stable in the bottle.

The chemistry has barely changed since the 1930s, which is why a modern polish and a pre-war one read almost the same on the label. What has changed is the law around it. In the European Union, Regulation (EC) No 1223/2009 decides which substances may be in the bottle and how the label must read, and two recent amendments have removed familiar names from gel systems.

What is nail polish made of?

A conventional nail polish is a nitrocellulose film former dissolved in volatile solvents, with plasticisers, resins, pigments and a suspending agent (Personal Care Magazine). Each ingredient class solves one problem. Take any one away and the polish either will not dry, will not bend, will not stick or will not show colour.

The order on the label follows weight. Solvents come first because they make up most of the liquid, then the film former, then plasticisers and resins, with pigments listed last under their colour index (CI) numbers. The rules for that order are set out in the guide to reading an INCI list.

How does nail polish dry into a film?

Solvent polish dries by evaporation, not by a chemical reaction. As butyl acetate and ethyl acetate leave the wet coat, the nitrocellulose chains that were floating in solution come closer together, tangle and lock into a continuous film. The film forms from the bottom up, because the solvent nearest the nail has the furthest to travel and the surface skins over last (Personal Care Magazine).

That bottom-up drying is the reason thin coats outlast thick ones. A thick coat forms a skin at the surface while solvent is still trapped underneath, so the film stays soft for hours and dents. Regular polish is touch-dry within minutes and takes several hours to harden fully. The full sequence, from wet coat to hard film, is covered in how nail polish works.

Gel polish is the exception. It contains no nitrocellulose and does not dry by evaporation. Acrylate monomers and oligomers are cured by a photoinitiator under a UV or LED lamp, which joins them into a cross-linked network. That difference in chemistry is why gel is regulated differently, as set out further down.

Why is nitrocellulose the film former in most polishes?

Nitrocellulose is cellulose from wood pulp or cotton that has been treated with nitric acid, which turns a fibre into a polymer that dissolves in esters and dries to a clear, hard, glossy film. It gives the film its hardness, toughness and resistance to abrasion, and on its own it is brittle, which is why it is always paired with plasticisers (Cosmetics and Skin).

Nitrocellulose lacquers came to nails from the varnish and lacquer trade. A New York company was making a nitrocellulose-based polish as early as 1903, and the DuPont car lacquers of the early 1920s are often cited as the source of the modern formula (Cosmetics and Skin; C&EN). The origin, grades and alternatives are covered in nitrocellulose in nail polish.

The main alternative is an acrylic polymer dispersion in water. Water-based polish has no flammable solvent and almost no smell, dries more slowly and has historically worn less well (Personal Care Magazine). The trade-offs are set out in water-based nail polish.

What do plasticisers and resins do?

A plasticiser is a small molecule that fits between the long nitrocellulose chains and keeps them from packing tightly, so the dried film can bend with the nail without cracking (Compound Interest). Camphor and castor oil were the plasticisers of the early polishes (Cosmetics and Skin). Modern lists use acetyl tributyl citrate, trimethyl pentanyl diisobutyrate, sucrose acetate isobutyrate or triphenyl phosphate.

A resin is a second polymer that improves adhesion to the keratin and adds gloss and depth. Natural resins were used until 1938, when synthetic toluenesulfonamide formaldehyde resin was introduced (Cosmetics and Skin). Today most polishes use a polyester such as adipic acid/neopentyl glycol/trimellitic anhydride copolymer, or tosylamide/epoxy resin.

Plasticiser and resin choice is where most of the free-from debate lives. Dibutyl phthalate was a common plasticiser until the EU prohibited it, and triphenyl phosphate (TPHP) is the plasticiser most often questioned today. What each of those substances did in polish and its legal status is covered in toluene, formaldehyde, DBP, camphor and TPHP explained.

Which solvents are in nail polish?

The solvents are the largest part of the bottle by weight and the part that leaves. Butyl acetate and ethyl acetate are the main pair: both dissolve nitrocellulose, both evaporate within minutes, and their ratio sets the drying speed (C&EN). Isopropyl alcohol is added as a diluent that thins the polish and lowers cost. The sweet, sharp smell of a fresh coat is the ester solvent, and it fades as the coat dries.

Toluene was once a standard solvent. In the EU it is restricted under Annex III, entry 185, of Regulation (EC) No 1223/2009 to nail products at a maximum of 25%, with the warnings Keep out of reach of children and To be used by adults only (EUR-Lex). Most brands sold in Europe have replaced it with acetates. Bio-sourced solvents, made by fermenting corn, cotton or cassava, are chemically the same esters from a different feedstock; how brands count them is covered in plant-based nail polish claims and natural origin percentages.

Where does the colour come from?

Colour comes from pigments, which are insoluble particles held in suspension, and from effect particles. Inorganic pigments include titanium dioxide for white and opacity, iron oxides for reds, browns and yellows, chromium oxide for green and ferric ferrocyanide for blue (Compound Interest). Organic pigments such as CI 15850 give the clean, bright reds and pinks. Shimmer comes from mica coated with titanium dioxide, and metallic and cat-eye effects come from aluminium or iron-oxide-coated flakes.

In the EU only colourants listed in Annex IV of Regulation (EC) No 1223/2009 may be used, and each appears on the label under its colour index number (EUR-Lex). Carmine (CI 75470) is made from cochineal insects and guanine from fish scales, which is why a vegan claim has substance in polish; the details are in vegan and cruelty-free nail polish.

Pigment settles unless something stops it. Stearalkonium hectorite, a modified clay, thickens the polish into a gel that thins as the brush moves and thickens again at rest, so glitter and pearl stay evenly dispersed in the bottle (C&EN). Benzophenone-1 or etocrylene is added as an ultraviolet absorber to slow fading in daylight.

Is nail polish scented, and why does it smell?

The smell of nail polish is the solvent, not a fragrance. Ethyl acetate and butyl acetate are both esters with a strong sweet odour that disappears once they have evaporated. A few brands add fragrance to mask it or to scent the dried film, and in the EU any of the listed fragrance allergens above the threshold must be named on the label under Article 19 of Regulation (EC) No 1223/2009 (EUR-Lex). Which polishes are scented and how allergen labelling works is covered in fragrance in nail polish.

Because the solvent is flammable and the smell is strong, polish should be applied in a ventilated room and stored with the cap tight. Old, thickened polish is household hazardous waste in most municipalities; the Dutch rules are in how to dispose of old nail polish.

What does EU law allow in nail polish?

Every cosmetic product sold in the EU falls under Regulation (EC) No 1223/2009. Annex II lists prohibited substances, Annex III lists restricted substances with their limits and warnings, and Annex IV lists the permitted colourants. Article 15 prohibits substances classified as carcinogenic, mutagenic or toxic to reproduction (CMR) in categories 1A and 1B, with narrow exceptions, and the Commission updates the annexes each time a new classification takes effect (EUR-Lex).

Three substances from the free-from lists are already prohibited or restricted this way. Dibutyl phthalate is Annex II entry 675. Formaldehyde was moved to Annex II, entry 1577, by Commission Regulation (EU) 2019/831 of 22 May 2019, which ended its use in nail hardeners (EUR-Lex). Toluene is restricted to 25% in nail products. In Europe a 3-free claim therefore describes the legal minimum. How the regulation, the responsible person and the notification portal work is set out in EU cosmetics regulation and nail polish.

The two gel rules

Two amendments apply to gel polish only. Commission Regulation (EU) 2020/1682 restricted hydroxyethyl methacrylate (HEMA) and di-HEMA trimethylhexyl dicarbamate to professional use, with the label warnings For professional use only and Can cause an allergic reaction, from 3 June 2021 for placing on the market (EUR-Lex). The allergy behind that rule is explained in HEMA allergy: gel versus regular polish.

Commission Regulation (EU) 2025/877 of 12 May 2025 added the photoinitiator trimethylbenzoyl diphenylphosphine oxide (TPO) to Annex II as entry 1731, applicable from 1 September 2025, after it was classified as toxic to reproduction category 1B (EUR-Lex). There is no sell-through period (European Commission). Solvent polish contains no photoinitiator, so the ban does not touch it. The full story is in the TPO ban in gel polish.

What do 3-free, 5-free and 10-free mean?

A free-from number counts the substances a brand has chosen to leave out. No regulator defines what 5-free or 10-free means, so each brand writes its own list. The common ladder starts with formaldehyde, toluene and dibutyl phthalate at 3-free, adds formaldehyde resin and camphor at 5-free, ethyl tosylamide and xylene at 7-free, and parabens, TPHP and other variable entries at 10-free and above.

Two things follow. First, a higher number is not a safer polish, because several of the added exclusions were never common in polish anyway. Second, in the EU a free-from claim must meet the common criteria for cosmetic claims in Regulation (EU) No 655/2013, and the Commission's Technical Document on claims advises against free-from claims for substances that are prohibited in any case (EUR-Lex). The full table and the reasoning are in 3-free, 5-free and 10-free explained.

Is nail polish safe to wear?

A polish sold legally in the EU has passed a safety assessment under Article 10 of Regulation (EC) No 1223/2009, carried out by a qualified assessor on the finished formula, and the dried film on a nail plate is a small, fixed exposure (EUR-Lex). The moments that matter are application and removal, when solvent is in the air and on the skin. Ventilation, short contact time and cuticle oil afterwards cover most of the practical risk.

Two groups deserve specific answers. Pregnancy raises questions about solvent exposure and gel lamps, and the sourced guidance is in nail polish during pregnancy. People with a diagnosed acrylate allergy should avoid gel systems and can usually wear solvent polish, because nitrocellulose lacquer contains no methacrylate monomer. Anyone with itching, swelling or blistering around the nails after a manicure should stop using the product and see a GP or dermatologist.

India Anaïs lacquers are solvent-based nitrocellulose formulas with no photoinitiator and no methacrylate monomer, which is why they need no lamp and fall outside both gel rules. The first edition is sold out, and the next edition is planned for spring 2027.