Hair coloring

Hair coloring is the practice of changing the hair color. The main reasons for this are cosmetic: to cover gray hair, to change to a color regarded as more fashionable or desirable, to restore the original hair color after it has been discolored by hairdressing processes or sun bleaching.

Hair coloring can be done professionally by a hairdresser or independently at home. Today, hair coloring is very popular, with over 75% of American women dyeing their hair. At home coloring in the United States reached $1.9 billion in 2011 and is expected to raise to $2.2 billion by 2016.

The dyeing of hair is an ancient art that involves treatment of the hair with various chemical compounds. In ancient times, the dyes were obtained from plants. Some of the most well known are henna (Lawsonia inermis), indigo, Cassia obovata, senna, turmeric and amla. Others include katam, black walnut hulls, red ochre and leeks. In the 1661 book Eighteen Books of the Secrets of Art & Nature, various methods of coloring hair black, gold, green, red, yellow, and white are explained. The development of synthetic dyes for hair is traced to the 1860s discovery of the reactivity of para- phenylenediamine (PPD) with air.Eugène Schueller, the founder of L'Oréal, is recognized for creating the first synthetic hair dye in 1907. In 1947 the German cosmetics firm Schwarzkopf launched the first home color product, "Poly Color". Hair dyeing is now a multibillion-dollar industry that involves the use of both plant-derived and synthetic dyes.

Hair color was traditionally applied to the hair as one overall color. The modern trend is to use several colors to produce streaks or gradations, not all work on top of a single base color. These are referred to as:

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