Hair coloring
Assyrian herbals dating back to 2177 BCE contain some of the oldest recipes for cosmetic preparations known, including hair dye.
[2] The ancient Egyptian Ebers Papyrus, c. 1550 BCE, has recipes for dyeing gray hair and eyebrows.
[6] Some of the most well known are henna (Lawsonia inermis), indigo dye, Cassia obovata, senna, turmeric, and amla.
Others include katam (buxus dioica), black walnut hulls, red ochre, and leeks.
[2] Diodorus Siculus, a Greek historian, described in detail how Celtic people dyed their hair blonde: "Their aspect is terrifying.
Their hair is blond, but not naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheads.
Some of them are clean-shaven, but others — especially those of high rank — shave their cheeks but leave a moustache that covers the whole mouth.
Trotula's De ornatu mulierum ("On Women’s Cosmetics"), from the 12th century, has multiple recipes for bleaching and coloring hair.
[10] The development of synthetic dyes for hair is traced to the 1860s discovery of the reactivity of para-phenylenediamine (PPD) with air.
[11] Eugène Schueller, the founder of L'Oréal, is recognized for creating the first synthetic hair dye in 1907.
Henna is an orange dye commonly used as a deposit-only[further explanation needed] hair color whose active component, lawsone, binds to keratin.
Indigo is natural dye from a plant (Indigofera tinctoria, I. suffructicosa, or I. arrecta) that can be added to henna or layered on top of it to create brown to black colors in the hair.
The dyes showed high buildup on hair and gave an intense blue color, which was stable to multiple washes.
Demi-permanent hair colors are not permanent but the darker shades in particular may persist longer than indicated on the packet.
Because it involves no developer (hydrogen peroxide) or ammonia, it is thus less damaging to hair strands than their demi-permanent counterpart.
The U.S. Environmental Protection Agency reported chronic exposure to PPD in the diet of rats and mice depressed body weight of the animals, with no other clinical signs of toxicity observed in several studies.
[18] Temporary hair color is available in various forms including rinses, shampoos, gels, sprays, and foams.
The color particles remain adsorbed (closely adherent) to the surface of the hair shaft and are easily removed with a single shampooing.
More recently, blacklight-reactive hair dyes have been brought to market that fluoresce under blacklights, such as those often used at nightclubs.
This means that they will only create the bright color of the packet if they are applied to light blond hair.
This involves mixing a small quantity of tint preparation and applying it directly to the skin for a period of 48 hours.
European dermatologists have, however, strongly advised against such pre-use testing, as it entails additional sensitisation (allergy) risk and the interpretation by lay people may not be sufficiently accurate.
That means that drips, slips and extra hair tint around the hairline can result in patches of discolored skin.
Ways of preventing skin discoloration are to wear latex or nitrile gloves to protect the hands and also by applying a thin layer of petroleum jelly or oil-based preparation around the hairline.
Acetone and nail polish remover are not considered effective; laundry detergent may sometimes work as may moist cigarette ash rubbed into the stained area.
[36] Synthetic permanent hair coloring requires three components: (1) 1,4-diaminobenzene (historically) or 2,5-diaminotoluene (currently), (2) a coupling agent, and (3) an oxidant.
The combination of hydrogen peroxide and ammonia causes the natural hair to be lightened, providing a "blank canvas" for the dye.
These dye intermediates and coupler compounds can undergo oxidation and coupling reaction as shown in the scheme below to form high molecular weight products, which are trapped in the hair matrix and cannot be readily removed through washing.
Various combinations of primary intermediates and coupler compounds provide a spectrum of shades of hair colors.
[40] As narrated in a hadith, the best thing with which to dye gray hair is henna and katam (a plant from Yemen which colors it black tinged with red).
