Hair coloring
Assyrian herbals dating back to the 7th century BCE contain some of the oldest recipes for cosmetic preparations known, including hair dye. These ancient clay tablets mention using the gall of a black ox, cypress oil, licorice, and honey to turn gray hair black. The ancient Egyptian Ebers Papyrus also holds recipes for dyeing gray hair and eyebrows. In ancient times, dyes were frequently obtained from plants like henna, indigo dye, Cassia obovata, senna, turmeric, and amla. Other natural sources included katam, black walnut hulls, red ochre, and leeks. Greek historian Diodorus Siculus described how Celtic people dyed their hair blonde by washing it in lime and combing it back from their foreheads. They looked like wood-demons with thick shaggy hair that resembled a horse's mane. Some Celtes were clean-shaven while others left a moustache covering the whole mouth.
English chemist William Henry Perkin accidentally discovered the first synthetic dye, mauveine, in 1856 while attempting to synthesize quinine as a treatment for malaria. His discovery marked the beginning of the synthetic dye industry and laid the groundwork for later innovations in hair dye chemistry. The development of synthetic dyes for hair is traced to the 1860s discovery of the reactivity of para-phenylenediamine with air. Eugène Schueller, the founder of L'Oréal, created the first synthetic hair dye in 1907. In 1947 the German cosmetics firm Schwarzkopf launched the first home color product called Poly Color. Hair dyeing has grown into a multibillion-dollar industry involving both plant-derived and synthetic dyes. At-home coloring in the United States reached sales of $1.9 billion in 2011 and was expected to rise to $2.2 billion by 2016. Between 50% and 80% of women in the United States, Europe, and Japan have reported using hair dye.
Foiling uses pieces of foil or plastic film to separate the hair to be colored when more than one color is applied. This method ensures that only the desired hair strands are colored while the rest remains spared. Balayage involves painting hair color directly onto sections without foils to keep the color contained. A balayage requires more precise hand-painting of hair sections and typically costs more than other methods. The difference between balayage and ombré lies in how precisely hair sections are painted. Baby lights create very thin highlights that result in natural and subtle effects. Splashlighting creates a horizontal band of bleached hair from ear to ear. Root touch-ups apply color only to the most recent section of re-growth, usually the first inch nearest the scalp. These root touch-ups repeat every 4 to 6 weeks as natural color grows in and becomes apparent. Block coloring applies two or more colors to create dimension and contrast in the hair.
Permanent synthetic dyes generally contain ammonia mixed with a developer or oxidizing agent to permanently change hair color. Ammonia opens the cuticle layer so that the developer and colorants can penetrate into the cortex. The developer comes in various volumes where higher volume produces greater lift of natural hair pigment. Someone with dark hair wishing to achieve two or three shades lighter may need a higher developer. Timing for permanent hair coloring typically lasts 30 minutes or 45 minutes for maximum color change. Synthetic permanent hair coloring requires three components: 1,4-diaminobenzene historically or 2,5-diaminotoluene currently, a coupling agent, and an oxidant. The process occurs under basic conditions involving oxidation of primary intermediates to quinone state. This diimine reacts with a coupler compound through electrophilic aromatic substitution. The final product oxidizes to give the finished dye trapped inside the hair matrix. Blue couplers include 1,3-diaminobenzene while red couplers include phenols and naphthols like 3-aminophenol. Yellow-green couplers include resorcinol which produces broad-band absorption for more natural-looking colors.
Phenylenediamine based hair dyes have been controversial and subject to many studies over recent decades. Several products have been removed from the marketplace due to safety concerns. Hair coloring can involve chemicals capable of removing, replacing, and covering up pigments naturally found inside the hair shaft. Use of these chemicals results in temporary skin irritation, allergy, hair breakage, skin discoloration, and unexpected hair color results. The International Agency for Research on Cancer states that some hair dyes and many chemicals used in the process are mutagenic and carcinogenic. Individuals allergic to gluten need caution since certain hair dyes include gluten even without ingestion. Symptoms of reactions include redness, sores, itching, burning sensation, and discomfort appearing hours or days after application. Salt lead acetate formerly the active ingredient in gradual darkening products is toxic and causes reproductive toxicity. Prolonged use of permanent dark hair dyes can double a person's risk of getting blood cancer types including leukemia and non-Hodgkin's lymphoma. In October 2017 Professor Kefah Mokbel published a meta-analysis showing hair dye use might increase breast cancer risk by 20% among users.
The European Union maintains particularly stringent health regulations regarding cosmetic compounds making contact with skin during application. To ensure hair dyes contain only safe substances, the European Commission adopted Directive 2012/21/EU restricting around 45 chemicals in hair dyes. This directive forms part of the general EU Cosmetics Directive 76/768/EC. Hair dyes are regulated in the commercial marketplace as new toxicity data generates for some ingredients. Health risks discovered over time have led to legal restrictions on certain hair dyes from the cosmetic marketplace. The U.S. Environmental Protection Agency reported chronic exposure to p-phenylenediamine in rats and mice depressed body weight without other clinical signs of toxicity. Para-Phenylenediamine is labeled as toxic and can cause adverse effects on aquatic organisms causing long-term environmental effects. European dermatologists strongly advise against pre-use patch testing since it entails additional sensitization risk. Interpretation by lay people may not be sufficiently accurate for determining allergic reactions before full product use.
Common questions
What ingredients did ancient Assyrians use to dye hair black?
Assyrian herbals from the 7th century BCE describe using gall of a black ox, cypress oil, licorice, and honey to turn gray hair black. These recipes appear on ancient clay tablets as some of the oldest known cosmetic preparations for hair dye.
When was the first synthetic hair dye created by Eugène Schueller?
Eugène Schueller created the first synthetic hair dye in 1907 while founding L'Oréal. This innovation followed William Henry Perkin's discovery of mauveine in 1856 and the development of para-phenylenediamine reactivity in the 1860s.
How often should people perform root touch-ups on their dyed hair?
Root touch-ups apply color only to the most recent section of re-growth usually within the first inch nearest the scalp. These applications repeat every 4 to 6 weeks as natural color grows in and becomes apparent.
Which chemicals are required for permanent synthetic hair coloring processes?
Synthetic permanent hair coloring requires three components including 1,4-diaminobenzene historically or 2,5-diaminotoluene currently along with a coupling agent and an oxidant. The process occurs under basic conditions involving oxidation of primary intermediates to quinone state.
What health risks does prolonged use of permanent dark hair dyes pose according to studies?
Prolonged use of permanent dark hair dyes can double a person's risk of getting blood cancer types including leukemia and non-Hodgkin's lymphoma. Professor Kefah Mokbel published a meta-analysis in October 2017 showing hair dye use might increase breast cancer risk by 20% among users.