Phenyl Methyl Pyrazolone

What Is It?

Phenyl Methyl Pyrazolone is a light yellow powder or a white powder or crystals. In cosmetics and personal care products, Phenyl Methyl Pyrazolone is used in the formulation of hair dyes and colors.

Why Is It Used?

Phenyl Methyl Pyrazolone imparts a 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

Phenyl Methyl Pyrazolone is used as an intermediate 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.

Safety Information

The safety of the Phenyl Methyl Pyrazolone has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that Phenyl Methyl Pyrazolone was safe for use as a hair dye ingredient.

CIR Safety Review:

Seven week feeding studies with Phenyl Methyl Pyrazolone showed no toxicity. A mixture containing 500 mg/kg of Phenyl Methyl Pyrazolone was, at most, a mild ocular irritant. Phenyl Methyl Pyrazolone was slightly irritating to skin when tested under occlusive patches. It did not produce a sensitization reaction. Phenyl Methyl Pyrazolone was nonmutagenic in two assays and noncarcinogenic in oral feeding studies. Phenyl Methyl Pyrazolone wass rapidly metabolized and readily detoxified.

More information about the safety of hair dyes.

Phenyl Methyl Pyrazolone and its salts may be used in oxidizing coloring agents for hair dye marketed in the European Union at a maximum concentration of 0.5%, or when used in combination with hydrogen peroxide, at a maximum use concentration upon application of 0.25% (see Annex III).

Link to the EU Cosmetic Regulation:

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 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. Phenyl Methyl Pyrazolone is a heterocyclic amine that functions as a hair colorant in cosmetics and personal care products.


The European Commission’s Scienific Committee on Consumer Products (SCCP) opinion concerning Phenyl Methyl Pyrazolone

EU Cosmetics Inventory

Search the FDA Code of Federal Regulations