What Is It?

p-Methylaminophenol Sulfate occurs as a colorless solid. In cosmetics and personal care products, p-Methylaminophenol and p-Methylaminophenol Sulfate are used in the formulation of permanent hair dyes, colors, and tints.

Why Is It Used?

p-Methylaminophenol and p-Methylaminophenol Sulfate 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

p-Methylaminophenol and p-Methylaminophenol Sulfate are primary intermediates used in permanent (oxidative) hair dyeing where color is produced inside the hair fiber. The color that is produced results from careful formulation of the product so that the ingredients interact in a highly controlled process.

Safety Information

The safety of p-Methylaminophenol and p-Methylaminophenol Sulfate has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that p-Methylaminophenol and p-Methylaminophenol Sulfate were safe for use as hair dye ingredients.

CIR Safety Review:

In skin absorption studies of radioactive p-aminophenol, as much as 11% of the radioactivity was found in the excreta, viscera, and skin. In subchronic and chronic dermal toxicity studies of hair dyes containing p-Methylaminophenol Sulfate, and other ingredients, no toxicologically significant differences were observed between the test subjects and controls. In an ocular irritation study, p-Methylaminophenol Sulfate was considered practically nonirritating to the eye and only slightly irritating to the skin and was not a sensitizer.

No significant embryotoxic or developmental effects were found when hair dyes containing p-Methylaminophenol Sulfate were administered. p-Methylaminophenol was not mutagenic in bacteria nor in the micronucleus assay and in the CHO chromosome aberration test. No statistically significant incidences of neoplasms, dermal and other, were found after 21 and 23 months of weekly dermal exposure to hair dyes containing p-Methylaminophenol Sulfate. When p-Methylaminophenol Sulfate was tested in 200 eczema patients without known previous contact with the ingredient, one patient had a positive reaction. 

More information about hair dyes.

p-Methylaminophenol and its salts are listed in the Cosmetics Directive of the European Union and may be used as oxidizing coloring agents for hair dyeing at a maximum concentration of 1.5% after mixing with hydrogen peroxide (See Annex III).

Link to the EU Cosmetic Regulation: http://europa.eu/legislation_summaries/consumers/product_labelling_and_packaging/co0013_en.htm

More Scientific Information

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 dye precursors are oxidized by the hydrogen peroxide to form reactive intermediates which then combine with the couplers resulting in 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. p-Methylaminophenol and p-Methylaminophenol Sulfate are substituted phenols that function as hair colorants. p-Methylaminophenol and p-Methylaminophenol Sulfate react with an oxidant to produce the corresponding imine, which then reacts with a coupler to form an indophenol dye.