4-Amino-2-Hydroxytoluene

Safety Information

Expert Panel for Cosmetic Ingredient Safety:

The safety of 4-Amino-2-hydroxytoluene has been assessed by the Expert Panel for Cosmetic Ingredient Safety. The Expert Panel evaluated the scientific data and concluded that 4-amino-2-hydroxytoluene was safe as used in hair dye products. In 2006, as part of the scheduled re-evaluation of ingredients, the Expert Panel considered available new data on 4-amino-2-hydroxytoluene and reaffirmed the above conclusion.

4-Amino-2-hydroxytoluene was poorly absorbed through the skin. In addition, 4-amino-2- hydroxytoluene had low oral toxicity and had no significant mutagenic or developmental effects. 4-Amino-2-hydroxytoluene demonstrated a weak potential for sensitization and was negative in photosensitization tests. A variety of epidemiology studies have given no indication of a carcinogenic effect from the use of hair dyes. The weight of the epidemiological evidence supports the safety of hair dyes.

More information about the safety of hair dyes.

In the European Union, 4-amino-2-hydroxytoluene may be used in hair dye products at a maximum concentration of 1.5% after mixing with hydrogen peroxide (see Annex III). Products containing 4-amino-2-hydroxytoluene must be labeled as indicated in Annex III.

Resources

FDA's fact sheet on Hair Dye Products
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Search the Code of Federal Regulations
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The European Commission's Scientific Committee on Cosmetic Products (SCCP) Opinion
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EU Cosmetics Inventory
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4-Amino-2-Hydroxytoluene


Chemical image provided by National Cancer Institute
What Is It?

4-Amino-2-hydroxytoluene is a substituted aromatic compound used in the formulation of permanent hair dyes, colors and tints.

Why Is It Used?

4-Amino-2-hydroxytoluene 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

4-Amino-2-hydroxytoluene 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.

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.