2,3-Naphthalenediol

Safety Information

Expert Panel for Cosmetic Ingredient Safety:

The safety of 2,3-naphthalenediol has been assessed by the Expert Panel for Cosmetic Ingredient Safety. The Expert Panel evaluated the scientific data and concluded that, although there was no evidence of hazard, additional data were considered to be desirable to support the safety of 2,3-naphthalenediol as a hair dye ingredient. When new data are available, the Expert Panel will reconsider the safety of this ingredient in hair dye products.

The Expert Panel concluded that the safety of 2,3-naphthalenediol has not been documented and substantiated. The Expert Panel requested additional data to complete the safety assessment for 2,3-naphthalenediol as it is used in hair coloring products. The data that were available indicated that 2,3-naphthalenediol was slightly irritating to the eye and was a sensitizer when tested at 1%. Test data indicated that 2,3-naphthalenediol was neither a mutagen nor a developmental toxicant. A formulation containing 0.1% 2,3-naphthalenediol was not a human skin irritant. The types of data required before the safety evaluation can be completed include dermal irritation, photosensitization, and sub chronic dermal studies, as well as chemical description and impurity data.

More information about the safety of hair dyes.

2,3-Naphthalenediol is listed in the Cosmetics Directive of the European Union and may not be used as a substance in hair dye products (see Annex II).

Resources

The FDA's factsheet on Hair Dye Products
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Search the FDA Code of Federal Regulations
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EU Cosmetics Inventory
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2,3-Naphthalenediol


Chemical image provided by National Cancer Institute
What Is It?

2,3-Naphthalenediol may be used in the formulation of permanent hair dyes, colors, and tints.

Why Is It Used?

2,3-Naphthalenediol helps to impart 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

2,3-Naphthalenediol may be 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.

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.