Hair oil

Hair dye is a product used to change the color of hair. It is commonly used for cosmetic purposes, to cover gray hair, to change to a color regarded as more fashionable or desirable, or to restore the original hair color after it has been discolored by hairdressing processes or sun bleaching.

History

The practice of changing the color of hair is ancient, dating back to ancient civilizations using plant-based dyes such as henna. In the 19th century, chemist Eugène Schueller developed the first synthetic hair dye, leading to the creation of the company L'Oréal.

Types of Hair Dye

There are several types of hair dye, which differ in their chemical make-up and duration of color:

• Temporary hair dye: These dyes cover the surface of the hair but do not penetrate into the hair shaft. They generally last until the next time the hair is washed.

• Semi-permanent hair dye: These dyes partially penetrate the hair shaft and generally last for a few weeks.

• Permanent hair dye: This type of dye penetrates the hair shaft and is resistant to fading, lasting until the hair grows out or is cut off.

Chemistry

Hair dye is a complex mixture of chemicals. The primary ingredient in most hair dyes is a colorless substance called para-phenylenediamine (PPD). When PPD is mixed with peroxide, it becomes an oxidizing agent, which is what allows the dye to penetrate the hair shaft.

Health Risks

There are potential health risks associated with the use of hair dye. Some people may have allergic reactions to the chemicals in hair dye, particularly PPD. There is also some evidence to suggest a link between long-term use of hair dye and an increased risk of certain types of cancer, although more research is needed in this area.

See Also

• Hair coloring
• Henna
• Hair bleaching