1-Naphthol

Safety Information

Expert Panel for Cosmetic Ingredient Safety:

The safety of 1-naphthol has been assessed by the Expert Panel for Cosmetic Ingredient Safety. The Expert Panel evaluated the scientific data and concluded that 1-naphthol was safe as a hair dye ingredient. In 2006, the Expert Panel considered available new data on this ingredient and reaffirmed the above conclusion.

The Expert Panel reviewed studies with 1-naphthol indicating that this compound at low concentrations was neither an eye nor skin irritant. No significant toxicity findings were reported in either sub chronic or chronic laboratory studies. Hair dyes containing this ingredient when dermally applied were neither developmental toxicants nor carcinogenic.

The Expert Panel recognized that clinical data for 1-naphthol were not available. However, hair dyes containing 1-naphthol are exempt from two provisions in the Federal Food, Drug, and Cosmetic Act of 1938 when cautionary statements and instructions for patch testing are displayed conspicuously on the labels. Therefore, the Expert Panel did not require clinical testing.

1-Naphthol and its salts are listed in the Cosmetics Directive of the European Union (see Annex III, Part I). 1-Naphthol and its salts may be used as oxidizing coloring agents for hair dyeing up to a maximum concentration of 2%, when combined with hydrogen peroxide. Products containing 1-naphthol and must be labeled as indicated in Annex III.

Resources

European Commission's Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers (SCCNFP)
Learn More
EU Cosmetic Ingredients Inventory
Learn More
Search the FDA Code of Federal Regulations
Learn More

1-Naphthol


Chemical image provided by National Cancer Institute
What Is It?

1-Naphthol is a clear, crystalline solid. In cosmetics and personal care products, it is used in the formulation of permanent hair dyes, colors and tints.

Why Is It Used?

1-Naphthol imparts color to hair. The exact color obtained will depend on the other ingredients that are used in the preparation and the starting color of the hair.

Scientific Facts

1-Naphthol is used in permanent hair coloring systems where color is produced inside the hair fiber. This is accomplished through careful formulation of the product so that the ingredients interact in a highly controlled process.

1-Naphthol is a polycyclic phenol that functions as a hair colorant by reacting with other ingredients. Hair dyeing formulations belong to three categories — temporary, semi-permanent and permanent coloring of hair. The permanent hair dyeing formulations are often referred to as oxidative hair dyes which are generally marketed as two-component products. One component contains the compounds (precursors) that become the colorants and the other component is a stabilized solution of hydrogen peroxide.

The two components are mixed immediately prior to use. The precursors and peroxide diffuse into the hair shaft, where color formation takes place after the ingredients combine to produce the coloring mixture. The precursors are oxidized by the hydrogen peroxide to form the colorant molecules. These molecules are too large to escape from the hair structure. The hydrogen peroxide in the oxidative hair dye product also serves as bleaching agent for the natural pigment of the hair. The color that is formed depends on the precursors and direct dyes present in the dyeing solution, pH of the dyeing solution and the time of contact of the dyeing solution with the hair.