Hair Dyes Types & Active Ingredients

A Technical Lesson on Hair Color Products & Hair Dyes

Hair dyes work more like paint by covering hair strands with chemical colors or by mixing with the melanin granules without altering them.

There are three basic categories :
1) permanent,
2) semi-permanent,
3) temporary.

Temporary form can be washed out instantly. As of now, permanent hair dyes are the most popular. They can be sub-divided into 1) oxidation hair dyes and 2) progressive hair dyes.

Oxidation hair dye products consist of dye intermediates and a solution of hydrogen peroxide. An example of dye intermediates is p-phenylenediamine which form hair dyes on chemical reaction. 2-nitro-p-phenylenediamine is another type of dye intermediates. They are already dyes and are added to achieve the intended shades. The dye intermediates and the hydrogen peroxide solution, often called the developer, are mixed shortly before application to the hair. The applied mixture causes the hair to swell and the dye intermediates penetrate the hair shaft to some extent before they have fully reacted with each other and the hydrogen peroxide and formed the hair dye.

The active ingredient for progressive hair dye products is lead acetate. In the U.S, the current regulation governs that lead acetate can be used as color additive for hair coloring as long as the concentration is less than 0.6% w/v. The most noticeable difference between oxidation and progressive hair dyes is that progressive dyes are intended to give a more gradual change in hair color.

Semi-permanent and temporary products are either in the form of aerosol spray, solutions or dry powders (or sometimes called fibers). The key ingredient is usually coal-tar carried by a vehicle that may consist of water, organic solvent, gums, surfactants, conditioning agents. In the US, the rules governing the quality of coal-tar dyes are confusing and there is no guarantee that the temporary or semi-permanent dye products you are using contain non-approved ingredients. Ethical manufacturers should always issue a caution statement in the packaging of their products advising consumers to do a small patch testing for skin sensitivity. Specifically, the US government suggests the following caution statement: "This product contains ingredients which may cause skin irritation on certain individuals and a preliminary test according to a accompanying directions should first be made. This product must not be used for dyeing the eyelashes or eyebrows, to do may cause blindness." The US government further indicates that the manufacturer will be subject to regulatory actions if the caution statement is not properly addressed and if their products are found to be harmful under customary use.

Clinical studies have shown that several coal-tar ingredients have been linked to cancer in animal testing. In particular, the U.S government issues warning that the ingredient 4-methoxy-m-phenylenediamine (4-MMPD, 2,4-diaminoanisole) will pose a material risk to human and should not be used in hair dye products without proper caution statement by the manufacturer.

In addition to 4-MMPD discussed above, the following ingredients are also found to have caused cancer in animal testing:
1) 4-chloro-m-phenylenediamine
2) 2,4-toluenediamine
3) 2-nitro-p-phenylenediamine
4) 4-amino-2-nitrophenol

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