INCI is the International Nomenclature of Cosmetic Ingredients, a standard naming system that gives every cosmetic ingredient one agreed name, so the ingredient list on a nail polish reads the same in every country where it is sold.
Also known as: INCI name, INCI list, ingredient list, International Nomenclature of Cosmetic Ingredients
The International Nomenclature of Cosmetic Ingredients (INCI) is the shared dictionary behind every ingredient list. Water is aqua, jojoba oil is Simmondsia chinensis seed oil, and the red iron oxide in a brick-red lacquer is CI 77491. One name per substance means a chemist in Rotterdam, a regulator in Brussels and a shopper in London all read the same word.
In the EU the list is a legal requirement. Article 19 of Regulation (EC) 1223/2009 says the ingredients on a cosmetic must be expressed using the common ingredient name from the glossary provided for in Article 33; where no common name exists, a term from a generally accepted nomenclature is used (EUR-Lex). Ingredients appear in descending order of weight, and those under 1 percent may be listed in any order after the rest. Nanomaterials carry the word nano in brackets, as in CI 77266 (nano) for carbon black in a black eyeliner.
The European Commission publishes the names in CosIng, its database of cosmetic substances, which also compiles the glossary of common ingredient names established under Decision (EU) 2019/701. CosIng is for information only: a substance appearing there is not thereby approved for cosmetic use, and only the Regulation itself decides what is allowed (European Commission).
For nail polish the useful names to recognise are nitrocellulose (film former), butyl acetate and ethyl acetate (solvents), acetyl tributyl citrate (plasticiser), triphenyl phosphate (a plasticiser many people avoid) and the CI numbers that identify each pigment. A plus or minus sign before a group of colourants means the shades in a range use some or all of them.