Toluene, formaldehyde, DBP, camphor and TPHP: what they did in polish and where the EU stands

Five names come up whenever nail polish and safety are discussed together. Toluene, formaldehyde and dibutyl phthalate were standard in polish until the mid-2000s and are the reason the phrase 3-free exists. Camphor is an older plasticiser. Triphenyl phosphate replaced dibutyl phthalate and is now questioned in its turn.

Each did a specific job in the bottle, drew a specific health concern, and has a specific legal status under Regulation (EC) No 1223/2009, the EU cosmetics regulation. Knowing all three turns a worrying list into a short reading exercise on the back of the bottle.

What did each substance do in nail polish?

Toluene is a solvent that dissolves nitrocellulose and resins and evaporates evenly, which gave older polishes a smooth, streak-free flow. Formaldehyde is a small reactive molecule that cross-links keratin, which is why it was used in nail hardeners; in polish it was present mainly as tosylamide/formaldehyde resin, a different substance that improves adhesion. Dibutyl phthalate (DBP) was the standard plasticiser, the ingredient that keeps the dried film flexible (Compound Interest).

Camphor is a plasticiser too, and one of the oldest: John Wesley Hyatt used it to plasticise nitrocellulose into celluloid in 1868, and camphor and castor oil were two of the commonest plasticisers in early polishes (Cosmetics and Skin). Triphenyl phosphate (TPHP) is the plasticiser many brands adopted when they removed DBP, and it also has a flame-retardant effect in a flammable liquid (Lab Muffin).

The entries come from the annexes of Regulation (EC) No 1223/2009 and its amendments (EUR-Lex; EUR-Lex, Regulation (EU) 2019/831).

Is toluene in nail polish dangerous?

Toluene affects the nervous system when inhaled in large amounts over time, which is why it is controlled in workplaces. In nail polish the question is whether the small amount that evaporates from a coat matters. The EU's Scientific Committee on Consumer Products reviewed the evidence in 2008 and concluded that toluene up to 25% is safe from the general toxicological view in nail cosmetics used as intended by adults, while flagging a foreseeable risk of increased inhalation by children playing with cosmetics sold as toys (SCCP opinion 1170/08).

That opinion is why the EU restricts toluene instead of prohibiting it. Annex III entry 185 of Regulation (EC) No 1223/2009 allows it in nail products only, at a maximum of 25%, with the warnings Keep out of reach of children and To be used by adults only on the label (EUR-Lex). Most brands sold in Europe have replaced it with butyl acetate and ethyl acetate, so toluene is rare on European shelves.

On a label, toluene appears under its own name, high in the list. If it is present, the two warnings must be present too.

Is formaldehyde still in nail polish?

Not in the EU. Formaldehyde was allowed as a preservative and, at higher levels, in nail hardeners until Commission Regulation (EU) 2019/831 of 22 May 2019 removed it from Annex V and Annex III and added it to Annex II as entry 1577. The Commission acted because formaldehyde had been classified as a category 1B carcinogen, and it prohibited it even though the scientific committee had concluded that hardeners with about 2.2% free formaldehyde could be used safely, because suitable alternatives existed (EUR-Lex).

Formaldehyde in polish was mostly a labelling confusion. The substance in most polishes was tosylamide/formaldehyde resin, a polymer made using formaldehyde that can release traces of it and is a recognised contact allergen. It remains permitted in the EU and is the substance 5-free lists exclude. Hardeners that once relied on free formaldehyde now use other cross-linkers such as dimethyl urea (Salon Geek).

On a label, look for Formaldehyde or Tosylamide/Formaldehyde Resin. The first should not appear on any product sold legally in the EU. People who react to the second can choose a polish with tosylamide/epoxy resin or a polyester copolymer instead.

Why was dibutyl phthalate banned?

Dibutyl phthalate is a phthalate ester that was the standard plasticiser in polish for decades. It was classified in the EU as toxic to reproduction, category 1B, on the basis of animal studies. Under the rule that later became Article 15 of Regulation (EC) No 1223/2009, substances classified as CMR 1A or 1B are prohibited in cosmetics, and DBP was added to the prohibited list in 2004 through Directive 2004/93/EC. It is now Annex II entry 675 (EUR-Lex).

The ban created the market for alternatives. Brands moved to triphenyl phosphate, to citrate esters such as acetyl tributyl citrate, and to trimethyl pentanyl diisobutyrate and sucrose acetate isobutyrate. The mid-2000s reformulations were the origin of the 3-free label, and the EU ban is why that label describes the legal minimum in Europe.

On a label, DBP appears as Dibutyl Phthalate. Other phthalates appear under their own names; none is common in polish today.

Is camphor in nail polish a problem?

Camphor is a plasticiser with a long history and a strong smell, the medicinal note some polishes have under the solvent. The concern is irritation: camphor can irritate skin and airways, and in high doses it is toxic if swallowed, which matters for a product children may reach. It is not restricted under the EU cosmetics annexes and remains permitted in polish.

Camphor's real disadvantage is technical. It is volatile, so it slowly leaves the film and the polish turns brittle with age. Most modern polishes use plasticisers that stay put.

On a label, camphor appears as Camphor, usually low in the list.

What is the concern about TPHP?

Triphenyl phosphate (TPHP) is the plasticiser most free-from lists miss, and the one with the most recent evidence. A 2016 study in Environment International recruited 26 participants, had them paint their nails with a polish containing about 1% TPHP, and measured diphenyl phosphate, TPHP's metabolite, in their urine. Levels rose nearly seven-fold 10 to 14 hours after painting, and the rise was much smaller when participants wore gloves, which pointed to uptake through the skin around the nail (Mendelsohn et al., Environment International 2016).

The concern is that TPHP shows hormone-related activity in laboratory studies. The cosmetic chemist Michelle Wong, reviewing the study, notes that the amounts measured are very small, the sample was small, and no health effect at these exposures has been shown (Lab Muffin). TPHP is permitted in EU cosmetics and is not listed in Annex II or III.

On a label, TPHP appears as Triphenyl Phosphate. A polish that has replaced it will show Acetyl Tributyl Citrate, Trimethyl Pentanyl Diisobutyrate or Sucrose Acetate Isobutyrate in the same position.

How to check a bottle for these five substances

You will need: the bottle or its product page and the full ingredient list, which by law is printed on the packaging or on a leaflet or card attached to it.

1. Read the first four names, the solvents. Butyl Acetate, Ethyl Acetate and Isopropyl Alcohol are the modern set; Toluene means the older solvent is present and the two warnings should appear on the pack.
2. Find the film former, Nitrocellulose, then the names that follow it. These are the plasticisers and resins.
3. Look for Triphenyl Phosphate or Camphor among the plasticisers. Their presence is legal; their absence tells you the brand has reformulated.
4. Look for Tosylamide/Formaldehyde Resin. If you have reacted to polish in the past, this resin is the most likely cause, and a polish with Tosylamide/Epoxy Resin or a polyester copolymer is the usual alternative.
5. Dibutyl Phthalate and Formaldehyde should not appear at all on a product sold in the EU. If they do, the product is non-compliant and can be reported to the national authority.

If skin around the nails itches, swells or blisters after polish, stop using the product and see a GP or dermatologist, who can arrange patch testing.