* Ancient times: People used plants and minerals to color their hair as far back as ancient Egypt, China, and India. Henna, derived from a plant, was (and still is) a popular choice.
* Mid-19th Century: The development of the first synthetic hair dye is credited to William Henry Perkin, an English chemist who accidentally created a mauve dye while trying to synthesize quinine in 1856. This discovery led to the development of other synthetic dyes.
* Late 19th and Early 20th Century: Eugène Schueller, a French chemist, is considered the founder of modern hair dye. In 1907, he created a safe hair dye formula called "Oréal" (later L'Oréal). This marked the beginning of the commercial hair dye industry as we know it.
So, while people have been coloring their hair for millennia, modern, commercially available hair dye has been on the market since the early 1900s, making it over a century old.