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Types of Hair Dye and Their Mechanisms of Action


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Hair color change by dye application is a common procedure among women. Hair dyes are classified, according to color resistance, into temporary, semipermanent, demipermanent and permanent. The first two are based on molecules which are already colored. Temporary dyes act through dye deposition on cuticles, but semipermanent may penetrate a little into the cortex and so the color resists up to six washes. Demipermanent and permanent dyes are based on color precursors, called oxidation dyes, and the final shade is developed by their interactions with an oxidizing agent, but they differ from the alkalizing agent used. In oxidation systems, there is an intense diffusion of the molecules into the cortex, what promotes a longer color resistance. Dyes and color precursors present differences related to chromophore groups, hair fiber affinity, water solubility, and photo stability. The aim of this review is to discuss the differences among hair dye products available in the market and their action mechanisms, molecular structures, application methods, and some aspects of formulations.
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Cosmetics 2015, 2, 110-126; doi:10.3390/cosmetics2020110
ISSN 2079-9284
Types of Hair Dye and Their Mechanisms of Action
Simone Aparecida da França, Michelli Ferrera Dario *, Victoria Brigatto Esteves,
André Rolim Baby and Maria Valéria Robles Velasco
School of Pharmaceutical Sciences, University of São Paulo, 05508-000 São Paulo, Brazil;
E-Mails: (S.A.F.); (V.B.E.); (A.R.B.); (M.V.R.V.)
* Author to whom correspondence should be addressed; E-Mail:;
Tel.: +55-11-3091-3623; Fax: +55-11-3815-4418.
Academic Editor: Enzo Berardesca
Received: 18 February 2015 / Accepted: 2 April 2015 / Published: 22 April 2015
Abstract: Hair color change by dye application is a common procedure among women.
Hair dyes are classified, according to color resistance, into temporary, semipermanent,
demipermanent and permanent. The first two are based on molecules which are already
colored. Temporary dyes act through dye deposition on cuticles, but semipermanent may
penetrate a little into the cortex and so the color resists up to six washes. Demipermanent
and permanent dyes are based on color precursors, called oxidation dyes, and the final
shade is developed by their interactions with an oxidizing agent, but they differ from the
alkalizing agent used. In oxidation systems, there is an intense diffusion of the molecules
into the cortex, what promotes a longer color resistance. Dyes and color precursors present
differences related to chromophore groups, hair fiber affinity, water solubility, and photo
stability. The aim of this review is to discuss the differences among hair dye products available
in the market and their action mechanisms, molecular structures, application methods, and
some aspects of formulations.
Keywords: hair; dye; temporary; semipermanent; permanent; action mechanism
Cosmetics 2015, 2 111
1. Introduction
The use of cosmetics in order to change hair color, such as hair dye products, occurs with high
frequency, mostly among the female population [1]. However, these hair dyes, due to their action
mechanisms, may cause serious damage to the hair fiber structure [2].
Throughout human history, many people have wished to change the appearance of their hair
because it was a way to differentiate the social status. Hair dye has been used since Ancient Egyptian
times when Rameses II reinforced red hair color using henna. In Ancient Greece, the hair was bleached
with a rinse of potassium solution and rubbed with a type of ointment made of yellow flower petals and
pollen [3]. Nowadays, hair dyes are in an important phase of development and since the Second World
War, great progress in discoveries and applications of new synthetic dyes has occurred.
Brazil is a country that, because of its high miscegenation, presents almost all the hair types.
Furthermore, because of the great importance that women give to their hair treatments, Brazil is now
the world leader in hair dye products [4]. Nevertheless, the dye market has focused on exports, mainly
to South American countries.
2. Composition and Morphology of Hair Fiber
Hair is an annex of the epidermis and covers the external tissues of most mammal. It is also
considered an adornment. It works as a thermal regulator and protects the head and the skin from the
sun due to the presence of melanin [5]. Humans have between 90 and 150 thousands of hair fibers on
the scalp that grow 1 cm/month (0.37 mm/day), and the normal amount of hair lost is between 50 and
100 fibers per day. The hair diameter varies from 15 to 110 μm, depending on the race [6]. Caucasian
hair is usually thin and fine, may have waves, and is circular under the cross-section view (ellipticity of
1.25). The African hair type (wavy to curly) has a larger diameter, with a slightly oval cross-section
(ellipticity of 1.75). Lastly, Mongolian hair also has a larger diameter but varies from flat to wavy with
a cross-section similar to Caucasian hair (ellipticity of 1.35) [7,8].
Hair or fur is composed of dead skin cells which pass through a keratinization process, derived from
hair or hair follicles that are invaginations that protrude into the dermis or hypodermis [9]. Keratin,
the main protein found in the hair fiber, is produced by the keratinocytes of the epithelial tissue
invagination. Small amounts of water-soluble substances are also present, such as pentene, phenols,
uric acid, glycogen, glutamic acid, valine and leucine [10].
The hair shaft is divided into four main distinct structures: cuticle, cortex, cell membrane complex
(CMC), and the medulla [11].
The cuticles (which consists of amorphous and protein material) are the most external part of the
hair strand and ensure chemical resistance. These cuticles carry out the function of regulating the
amount of water in the hair structure, which keeps its physical properties. It contains six to ten layers
of overlapping cells in the longitudinal direction of the fiber [12]. The damage to the cuticle can be
caused by weather or mechanical friction such as combing and brushing. The excessive use of
shampoo and other inappropriate cosmetics may damage hair [13]. Each cuticle cell contains an
external thin membrane (5.0 to 10.0 nm) probably formed by a layer of fatty acid connected to the
Cosmetics 2015, 2 112
protein layer through thioester bonds, which generates cysteine residues responsible for the apparent
hydrophobic character of the fiber [12].
The cuticle contains three important layers: the A-layer (120 nm) with a high content of cysteine
and highly cross-linked; the exocuticle (B-layer), also rich in cysteine and occupying about the half of
the cell volume; and, finally, the endocuticle, a layer with a low content of cysteine and relatively high
levels of basic (lysine, arginine) and diacids (aspartic and glutamic acids) amino acids [7,14].
The cortex is the principal component of the hair, consisting of cylindrical cells of about 1 to 6 μm
of thickness and 100 μm of length. It forms the matrix where other proteins and keratin are located,
and composes the larger part of the fibrous mass of human hair, being formed by intracellular and
intercellular material [15]. The cortex represents 90% of its total weight and consists of cells filled
with keratin, with an organization that provides mechanical properties to the fibers [16]. The cortical
cells, adjacent to the cuticle, are flatter and contain less sulfur than the cells inside the cortex, which are
rich in cystine (two cysteine), amino acids, lysine and histidine, in addition to the melanin granules [7].
The matrix comprises the major structure of the hair and contains a high concentration of disulfide
bonds. It presents considerable swelling when in contact with water and forms a lightly cross-linked
gel structure. Although there are amorphous regions, the matrix presents small parts with structural
organization [17]. It exhibits keratin macrofibrils aligned in the direction of the hair strand and melanin
granules which are responsible for the hair color and its photo protection.
The CMC is an important layer in the hair structure consisting of cell membranes and adhesive
material that “glue” or link the cortical and the cuticle cells. Chemically, CMC is composed of
proteins, polysaccharides, and ceramides. It is also responsible for the hair’s natural moisture, making
it bright, transparent, and hydrated [6]. Its outer lipid layer forms the epicuticle and the inner lipid
layer is located between the cuticle cells which consist of the δ-layer, formed by proteins with a low
content of cystine (<2%) and richer in polar amino acids (12% basic and 17% acid). The CMC and the
endocuticle are usually referred to as non-keratinized regions because they have a low level of sulfur
amino acids and studies have proven that they are important pathways to the diffusion of molecules to
inner regions of the hair fiber [7].
The medulla is the innermost region and its presence along the hair is usually discontinuous or even
absent and does not interfere with the hair structure [11]. The medulla can be empty or filled with
sponge keratin, can serve as a pigment reservoir, and can contribute to the brightness of the hair.
The lipid concentration inside the medulla is bigger than anywhere else in the hair [18].
3. Hair Dyes
Hair dying systems can be divided into two main categories, oxidative or non-oxidative, and also
according to the color durability after the application on hair strands: temporary, semipermanent,
demipermanent and permanent [10,19].
Many studies established the diffusion path of the dye molecule to the inner hair fiber. It involves
the permeation of the molecules into intercuticular regions, passing through non-keratinized regions of
the endocuticle and the intracellular cement. In later stages, it migrates to keratinized regions and,
eventually, reaches the macrofibrils, before being incorporated into the matrix [7].
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The temporary and semipermanent non-oxidative dyes are based on colorful molecules, named dye
deposition, because the dye molecule only interacts with the hair cuticles. When there is a small
penetration of the molecules into the hair cortex, they are named semipermanent products and can be
resistant up to six washes. The demipermanent and permanent oxidative are based on precursors,
named oxidation dyes, whose color characteristics are developed by means of the interaction with an
oxidizing agent, and present longer lasting color [20].
3.1. Temporary Non-Oxidative Hair Dyeing
The temporary non-oxidative dyeing has a reduced permanence time on the fiber, leaving the hair
after the first shampoo washing because dye presents high molecular weight and deposits on the hair
surface without the capacity of penetrating the cortex [15]. This type of dye does not have the power of
whitening the hair strand and, therefore, it is indicated only to add new nuance and not to change its
color [1]. In white, blond or bleached hairs, it is possible to add a new color with a more noticeable
effect because the hair strand’s background color allows the visualization of the new applied color.
The temporary dye can be used for specific purposes such as adding colorful reflections, removing
the yellowish effects of the white hair, and covering a small quantity of white hair [21]. It allows the
dyeing of hair containing up to 15% white hair, due to their ability to deposit on the hair strands.
These dyes, that present acid characteristics [22] usually have high molar mass, according to the
structures presented in Table 1. They contain anionic characteristics and are selected to allow the
maximum solubility in water and the minimum penetration in hair so it is removed in the first
washing [17]. They are presented as shampoo, gel, emulsion and solution (liquid) with two different
forms of application: continuous application (progressive) or single application, with one wash at the
end of the application process to remove the unabsorbed dye excess on the hair strand.
Table 1. Structural and molecular formulas of acid dyes used in temporary non-oxidative
dye formulation [23]. Legend: INCI, International Nomenclature of Cosmetic Ingredients;
CAS, Chemical Abstract Service.
INCI: Acid Yellow 23 INCI: Acid Orange 7
CAS No. 1934-21-0
EINECS No. 217-699-5
Formula: C16H12N4O9S2·3Na
Chemical Classification: pyrazol
CAS No. 633-96-5
EINECS No. 211-199-0
Formula: C16H12N2O4S·Na
Chemical Classification: monoazo
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Table 1. Cont.
INCI: Acid Yellow 1 INCI: Acid Red 33
CAS No. 846-70-8
EINECS No. 212-690-2
Formula: C10H6N2O8S·2Na
Chemical Classification: nitro
CAS No. 3567-66-6
EINECS No. 222-656-9
Formula: C16H13N3O7S2·2Na
Chemical Classification: monoazo
INCI: Acid Red 92 INCI: Acid Violet 43
CAS No. 18472-87-2/4618-23-9
EINECS No. 242-355-6
Formula: C20H4Br4Cl4O5·2Na
Chemical Classification: xanthene
CAS No. 4430-18-6
EINECS No. 224-618-7
Formula: C21H15NO6S·Na
Chemical Classification: anthraquinone
INCI: Acid Blue 9 INCI: Acid Black 1
CAS No. 3844-45-9
EINECS No. 223-339-8
Formula: C37H36N2O9S3·2Na
Chemical Classification: triphenylmethane
CAS No. 1064-48-8
EINECS No. 213-903-1
Formula: C22H14N6O9S2·2Na
Chemical Classification: diazo
Cosmetics 2015, 2 115
Frequently, two to five substances are necessary to reach the desired hair color because just one
substance does not achieve natural shades. Some formulations use two molecules to remove the
yellowish effect in white hair and also four to five substances are mixed to reach the red, brown, and
black shades [17].
The temporary non-oxidative formulations as single applications, present higher dye concentrations,
ranging from 0.1% to 2.0% (w/w) and have the purpose of promoting a stronger dyeing effect.
However, the limit of deposition must be always respected because this type of application will not
cover gray hair satisfactorily in people with more than 30% of white hair fibers. The formulation must
get in contact with hair for about 30 min and results will occur immediately. It is suitable for those
who wish for fantasy colors [24]. It resists from three to six washes when applied to bleached hair,
like semipermanent dyeing.
3.2. Semi-Permanent Non-Oxidative Hair Dyeing
These formulations contain basic or cationic dyes with low molar mass, which has a high affinity
for hair keratin and resists from three to six washes [10]. The hair dyeing process does not involve
oxidation reaction; the application is simple and lasts from 10 to 40 min, followed by rinsing [1,25].
Several products are available in the market: lotions, shampoos, mousses and emulsions. These
cosmetic forms must have the ideal viscosity so that they do not flow during the application [20]. Dyes
with low molar mass penetrate slightly in the cortex, especially because of the high pH value of the
product that promotes the cuticles opening [15].
Demipermanent hair products promote major hair color durability (resistance up to 20 washes)
because they consist of a mix of semipermanent molecules with oxidation dye precursors, applied with
hydrogen peroxide (H2O2) [20].
Another option of formulation involves mixing nitro aniline dyes with basic or acid dyes which aim
for a better color result and a bigger resistance to washes, considering the high affinity of the two
families of dyes. The hair space not filled with the basic dyes will be occupied by nitro anilines,
thus promoting a much more uniform color in the first application. Table 2 contains the molecules
allowed and used in cosmetic formulations for semipermanent hair dyeing.
The nitro anilines are molecules comprised of a neutral aromatic amine or anthraquinone derivatives
and all are classified as highly polar and present mono, di, or tri nuclear rings. These dyes are diffused
through the hair fiber and are retained by weak Van de Waals bonds [17]. Under similar conditions, the
larger molecules with tri aromatic rings are removed more slowly from hair than the smaller,
mononuclear ones [26].
The cationic dyes shown in Table 3 are used in both temporary and semipermanent dyeing.
They permit reflective effects and are excellent for instantaneous color effects. The similarities
between the size of the cationic molecules grant substantivity to the hair in a homogenous way,
ensuring the color reproducibility and the resistance to washing uniformly. In other words, all dyes are
removed simultaneously during this process [24].
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Table 2. Structural and molecular formulas of nitro anilines used in semipermanent hair
dyeing formulation [23]. Legend: INCI, International Nomenclature of Cosmetic
Ingredients; CAS, Chemical Abstract Service; HC, Hair Color.
INCI: HC Yellow No. 2 INCI: HC Red No. 3
CAS No. 4926-55-0
EINECS No. 225-555-8
Empirical Formula: C8H10N2O3
Chemical Classification: nitro aniline
CAS No. 2871-01-4
EINECS No. 220-701-7
Empirical Formula: C8H11N3O3
Chemical Classification: nitro aniline
INCI: 4-hydroxypropylamino-3-nitrophenol INCI: N,N'-bis-(2-hydroxyethyl)-2-nitro-
CAS No. 92952-81-3
EINECS No. 406-305-9
Empirical Formula: C9H12N2O4
Chemical Classification: nitro aniline
CAS No. 84041-77-0
EINECS No. 281-856-4
Empirical Formula: C10H15N3O4
Chemical Classification: nitro aniline
INCI: HC Blue No. 2
CAS No. 33229-34-4
EINECS No. 251-410-3
Empirical Formula: C12H19N3O5
Chemical Classification: nitro aniline
Cosmetics 2015, 2 117
The good performance of semipermanent dyes is directly related to their great water solubility.
In general, the nitro anilines are not soluble in water and require a glycol or glycol derivative, such as
glycerin, to be solubilized in the formulation. Specific solvents, such as mixtures of quaternary salts of
high molecular weight, such as Quaternium-80, benzyl alcohol, and glycols are used to ensure not only
their solubility in the formulation but also during application and product storage [24,27].
Cationic dyes exhibit excellent affinity for damaged hair, because positive sites of the dye molecule
bind to negative sites on the hair fiber by an ionic bond [28]. They allow greater resistance to washing
when compared to nitro anilines.
Table 3. Structural and molecular formulas of cationic dyes used in semi-permanent hair
dyeing formulation [23]. Legend: INCI, International Nomenclature of Cosmetic
Ingredients; CAS, Chemical Abstract Service.
INCI: Basic Red 51 INCI: Basic Red 76
CAS No. 77061-58-6
EINECS No. 278-601-4
Empirical Formula: C13H18N5·Cl
Chemical Classification: direct dye
CAS No. 68391-30-0
EINECS No. 269-941-4
Empirical Formula: C20H22N3O2·Cl
Chemical Classification: direct dye
INCI: Basic Brown 16 INCI: Basic Brown 17
CAS No. 26381-41-9
EINECS No. 247-640-9
Empirical Formula: C19H21N4O·Cl
Chemical Classification: direct dye
CAS No. 68391-32-2
EINECS No. 269-940-0
Empirical Formula: C19H20N5O3·Cl
Chemical Classification: direct dye
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Table 3. Cont.
INCI: Basic Blue 99 INCI: Basic Yellow 57
CAS No. 68123-13-7
EINECS No. 268-544-3
Empirical Formula: C19H20BrN4O2·Cl
Chemical Classification: direct dye
CAS No. 68391-31-1
EINECS No. 269-943-5
Empirical Formula: C19H22N5O·Cl
Chemical Classification: direct dye
The cationic dyes are water-soluble; however, they also require the addition of solvents to ensure
the homogeneity of the color and prevent recrystallization during storage because, in recrystallized
form, the molecule does not provide the cationic sites to bind to hair strands [24].
The pH control is essential for color stability. A weak base such as mono ethanolamine must be
added to achieve a pH of 9.0, and then a weak acid such as 10% citric solution is used to lower the pH
value to 6.0. This way, a buffer system which ensures the pH maintenance of the finished product
during shelf life is formed [24].
Other dyes, such as metallic and vegetables derivatives, are also considered to be semipermanent
dyes and can be used in hair dyeing. Henna is the most widely used vegetable dye for hair, promoting
reddish orange color shades [1,25]. In some commercial products, it is mixed with other dyes to
increase the range of color. It consists of the dried leaves of the Lawsonia alba plant, growing in North
Africa, in the Midwest, and in India [19,20]. Its coloring properties are due to the presence of the
substance 2-hydroxy-1,4-naphthoquinone, soluble in hot water and substantive to hair keratin in
pH 5.5 [10,29].
Another vegetable dye commonly used to obtain yellow shades is chamomile [1] that promotes
greater light reflection. Of all the species of chamomile, only Anthemis nobilis (Roman Chamomile)
and Matricaria chamomillae (German chamomile) have cosmetic applications, and both are
substantive to hair. The active ingredient of the flowers is 1,3,4-trihydroxyflavone, also known as
apigenin [10].
The metallic dyes are derived from silver salts, lead, and bismuth and are traditionally used by men
because the dyeing effect is not immediate and does not promote 100% of the white hair coverage.
The darkening of the hair strands occurs gradually, promoting a more natural appearance, which
satisfies the general public. The use is limited to the number of gray hair strands [1]. Therefore, hair
with a lot of white fibers cannot have a satisfactory result because of the leak of homogeneity in the
final color.
Products containing diluted lead acetate are applied to the hair daily and do not require washing,
so the metal salt is exposed to air oxygen and also reacts with sulfur from keratin. These reactions
Cosmetics 2015, 2 119
generate a mixture of metallic oxides and insoluble sulfides [10], responsible for gradual darkening of
gray hair [20].
A disadvantage of the metallic dyeing process is the lack of control in the color progression because
of the composition of hair, which is based on keratin. The keratin reduction will result in different
colors, so after the first applications, hair can present greenish or yellowish shades. However, the final
result is natural because the color develops progressively to more usual shades, such as brown and
black, and coverage of 100% of white hair strands is impossible.
3.3. Permanent Oxidative Hair Dyeing
The permanent hair dyes are commonly used [1] because this category provides greater efficacy of
permanent dyeing, resistance to shampoo washes and other external factors, such as drying, friction,
light, and others. This category represents about 80% of the sold hair dyes [10] and gets any shade,
covering up to 100% of white hair strands. Also, it is possible to have dark and light natural hair color [21]
due to the combination of the oxidizing agents with the ammonia hydroxide. The principal difference
between the demipermanent hair dye in comparison with a permanent one is the alkalizing agent used
because, in the first, monoethanolamine with low color lightening power is used [28].
Color formation happens upon mixture and involves complex reactions between precursors in the
presence of an oxidizing agent [20]. The precursors can be classified into two categories: oxidation
basis or primary intermediaries, and the couplers or reaction modifiers [10].
The reaction occurs in an alkaline medium that promotes the opening of the cuticles that allows the
penetration of the dyes’ molecules into the cortex. The oxidizing agent permits the beginning of the
reaction that occurs in the cortex and results in a colorful complex with high molar mass, which avoids
the exit of molecules formed in the hair. Part of the reaction also happens on the cuticles and the
molecules are removed in the first washes [30,31].
The ammonia hydroxide and ethanolamines are the most alkalizing agents used. A mixture of
surfactants and solvents is used to disperse the dye molecules and ensure the hair wetting. A small
amount of reducing agent is added to prevent auto-oxidation of the dyes during storage of the finished
product [20], which may be formulated as an emulsion, gel, solution and powder.
The reactions involved in the formation of permanent dyes are redox types and require four major
components: the aromatic amine with substitutions at positions ortho or para (hydroxy or amino) as
the coupling bases; the reaction modifiers; an alkalizing compound; and an oxidizing agent.
3.3.1. Coupling Bases
Bases are aromatic compounds derived from benzene, substituted by at least two electron donor groups
such as NH2 and OH in para or ortho positions to confer the property of easy oxidation [10], acting as a
color developer [28]. Two major compounds are used such as p-phenylenediamine (Scheme 1) and
p-aminophenol (Scheme 2).
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Scheme 1. Structural formula of p-phenylenediamine (PPD). INCI name: phenylenodiamine.
CAS No. 106-50-3. EINECS No. 203-404-7. Formula: C6H8N2. Chemical classification:
aromatic amine [23]. Legend: INCI, International Nomenclature of Cosmetic Ingredients;
CAS, Chemical Abstract Service.
Scheme 2. Structural formula of p-aminophenol (PAP). INCI name: p-aminophenol.
CAS No. 123-30-8. EINECS No. 204-616-2. Formula: C6H7NO. Chemical classification:
substitute phenol [23].
3.3.2. Reaction Modifiers
Reaction modifiers, also called couplers, are aromatic compounds derived from benzene and
substituted by groups such as NH2 and OH in the meta position, which does not present easy oxidation
by H2O2 [10]. They do not produce significant color alone but can modify them when used as primary
intermediaries and oxidants [28]. There are many reaction modifiers available in the market, and some
of the most important are shown in Table 4.
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Table 4. Molecular and structural formulas of reaction modifiers [23]. Legend: INCI,
International Nomenclature of Cosmetic Ingredients; CAS, Chemical Abstract Service.
INCI: 4-chlororesorcinol INCI: 2,4-diaminophenoxyethanol HCl
CAS No. 95-88-5
EINECS No. 202-462-0
Empirical Formula: C6H5ClO2
Chemical Classification: halogenated phenol
CAS No. 66422-95-5
EINECS No. 266-357-1
Empirical Formula: C8H12N2O2·2HCl
Chemical Classification: aromatic amine salt
INCI: 2-amino-hydroxyethylaminoanisole sulfate INCI: 4-amino-2-hydroxytoluene
CAS No. 83763-48-8
EINECS No. 280-734-8
Empirical Formula: C9H14N2O2·H2O4S
Chemical Classification: aromatic amine salt
CAS No. 2835-95-2
EINECS No. 220-618-6
Empirical Formula: C7H9NO
Chemical Classification: aromatic substitute
INCI: m-aminophenol INCI: Resorcinol
CAS No. 591-27-5
EINECS No. 209-711-2
Empirical Formula: C6H7NO
Chemical Classification: substitute phenol
CAS No. 108-46-3
EINECS No. 203-585-2
Empirical Formula: C6H6O2
Chemical Classification: phenol
3.3.3. Alkalizing Compounds
The addition of alkalizing compounds is necessary for the process of hair dyeing to promote the
proper pH value for the beginning of the oxidation reaction. The most commonly alkalizing
compounds used are ammonia, in the form of ammonium hydroxide, and monoethanolamine, when the
formulation contains water, or sodium silicate when it is in solid form (powder).
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When ammonia is used, it is possible to cover 100% of white hair and to remove the natural
pigments present in hair as the melanin. This type of dye is considered permanent because, after the
formation of the colored polymer in the inner of the cortex, its complete removal is not possible.
However, some polymers formed from the reaction between couplers and precursors can be eliminated
by reducing agents such as sodium hydrosulfite [10].
The addition of monoethanolamine (MEA) is required to maintain optimum alkaline pH for the
reaction. However, this substance does not oxidize the melanin. Thus, products containing MEA
instead of ammonia hydroxide are suitable for maintenance of similar shades or to dark hair [24].
3.3.4. Reducing Agents
Reducing agents are added to oxidative dye formulations to retard the reaction between bases and
reaction modifiers and to prevent the initiation of the reaction in the packaging tube during the storage
time. One of the molecules most used for such applications is sodium metabisulfite (MBS).
3.3.5. Antioxidants
Antioxidants are necessary to avoid the reaction beginning before the addition of the oxidant itself.
It is recommended to use a water-soluble antioxidant because the manipulation of bases and reaction
modifiers could initiate the oxidative reaction, which may interfere with the final color of the product.
One of the molecules most frequently used for this purpose is the erythorbic acid (AEB). It is also
recommended to use an oil-soluble antioxidant when emulsion is used as a vehicle for hair dyes
because this avoids the yellowing of wax and the oxidation of bases and reaction modifiers. One of the
most used molecules is T-butylquinone (TBQ) [24].
3.3.6. Oxidants
There are basically two types of oxidants used: hydrogen peroxide, when the vehicle is water, and
sodium persulfate, when it is a powder. The peroxides are very unstable, requiring the use of stabilizers
such as sodium stannate and the pentasodium pentetate [24]. They are usually used in the form of
emulsion, so-called “creamy hydrogen peroxide”.
3.3.7. Vehicles
The oxidative dye in the form of emulsion is the highest selling product in the market, but other
carriers are available such as gels, solutions (liquid), and powders. The preparation of the emulsion
begins with adding the dye mixture to the reducing agents, antioxidants, and ammonium hydroxide in
20% of the aqueous phase. The other 80% of water is added in a manufacturing tank and heated to
70 °C under constant agitation. After reaching the temperature, all the wax and the emulsifying agents
are added, maintaining a constant stirring until cooling to 40 °C, when the remaining 20% of the water
previously prepared is added. It is recommended to measure the ammonia content at the end of the process
and to ensure that the amount of alkalizing is sufficient to complete the reaction after 24 h. Because it is
very volatile, a small amount of ammonia can be lost during the process, so an adjustment is necessary
before packaging [24].
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3.3.8. Hair Color Formation
Bandrowski’s base (Figure 1) may be formed during the color formation process by the reaction of
p-phenylenediamine (PPD) coupling base in alkaline medium containing hydrogen peroxide [32].
It is a compound that reacts preferentially with the modifiers presented in Table 4 for the formation of
colored compounds which rise gradually. This reaction occurs in stages until the final formation of the
color, so the amounts of coupling bases and modifiers vary with the desired final color [33]. About 3%
to 5% of PPD becomes a Bandrowski’s base, which is present in most oxidation reactions but does not
affect the final hair color [34].
Figure 1. Bandrowski’s base. CAS No. 20048-27-5. Formula: C18H18N6 [33].
The intermediate compounds have similar sizes and, therefore, an easy and uniform penetration
occurs inside the hair [34]. The critical diameter size of the molecules for this penetration to occur is
6.0 Å, because the intermediates, in most cases, vary from 4.7 to 5.6 Å [35]. The color formation is
based on a series of oxidation and coupling reactions, divided into three main stages:
(a) Quinonamines formation: is the oxidation of low reactivity bases with hydrogen peroxide
under alkaline conditions with the formation of monamines from para and ortho-aminophenols, and
diamines from p-phenylenediamine and o-phenylenediamine. The PPD is especially oxidized in a
reactive intermediate, the quinoamine that, in the presence of the reaction modifier, will generate a
colorful polymer [33].
(b) Diphenylamines formation: cations of quinones formed in the first stage receive an addition of
couplers to form a substituted p-phenylenediamine.
Nucleophilic compounds including meta couplers and para non-oxidized bases act as couplers
because they react with the nitrogen atom of amine-quinones. As an example, there is the formation of
diphenylamines from the reaction of p-phenylenediamine with m-phenylenediamine [24]. Thus, a full
range of substituted diphenylamines from other para bases amine-quinones and other non-oxidative
bases may be formed.
Cosmetics 2015, 2 124
(c) Color formation: Diphenylamines formed can be considered as new oxidation bases, in which
one of the benzene rings are tri substituted (1,2,4 or 1,2,5 positions) by electron donor groups. Because
of this, they have the same potential, possibility of oxidation, and coupling capacitance that the
original para bases from which they are derived [10].
The intermediate compound formed in these p-phenylenediamine trimers is Bandrowski’s base
which is considered a primary intermediate in the color formation. The process occurs at a slow rate in
the presence of hydrogen peroxide (30 to 45 min), which is interesting for the penetration of these
intermediates in the cortex. The molecules are initially small in size and are then transformed into
Bandrowski’s base with greater size than those that do not have a satisfactory penetration [35].
Various parameters may affect the color formation in the hair dyeing process, such as pH, pause
time, hair keratin, and purity of the dye molecule, amongst others.
The variation of the pH value directly influences the reaction rate because a more alkaline pH
favors the reaction and facilitates the cuticle opening, allowing the penetration of molecules into the
cortex [28].
The pause time is essential for a complete reaction between the bases and reaction modifiers to
occur. According to the manufacturer’s guidelines, the product must be in contact with the hair from
30 to 45 min after application because it is then possible to ensure color reproduction and durability to
washing. The removal of the product in a shorter time can stop the reaction before it is complete,
creating a variance in the final color [24].
4. Conclusions
Among the various options of hair dyes, it is interesting to know the application features and their
affinity for the hair fibers in order to select the best option for each hair type and to provide a satisfactory
effect, as a good covering power of gray/white hair, good color resistance to shampoo washes, and high
durability of color. The challenge is to find options that provide security in the application and allow
these benefits to occur without generating very aggressive damage to the hair strands.
We thank Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for financial support
(FAPESP Process: 2013/16070-8).
Author Contributions
Simone Aparecida da França and Michelli Ferrera Dario wrote the paper; Victoria Brigatto Esteves
drew all images; André Rolim Baby and Maria Valéria Robles Velasco reviewed the paper.
Conflicts of Interest
The authors declare no conflict of interest.
Cosmetics 2015, 2 125
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© 2015 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
... Among the types of semi-permanent hair dye the basic hair dye is a hair dye consisting cationic, basic pigments (Massoni, 2004). Basic hair dye is a direct dye which does not need PPD, hydrogen peroxide, nor alkali to color the hair (França et al., 2015;Hehner et al., 2002). While the color of permanent hair dye is produced inside the cortex of hair by the oxidation reaction, basic hair dye applies the basic (cationic) pigment on the hair in its colored form (Tucker, 1971). ...
... While the color of permanent hair dye is produced inside the cortex of hair by the oxidation reaction, basic hair dye applies the basic (cationic) pigment on the hair in its colored form (Tucker, 1971). Basic hair dye do not cause oxidative damage to hair and skin and the dyeing method is simple (França et al., 2015;Hehner et al., 2002). ...
... The European Commission's Scientific Committee on Consumer Safety (SCCS) defined that Basic Brown 16 is a direct pigment which can be used without oxidizing and can be used up to 2.0% concentration on the head (Scientific Committee on Consumer Safety, 2013). França et al. (2015) explained that the pH control of basic hair dye is a must for the stability of the color. And a number of research implied that the pH of the dye might have an effect on the color or the dyeability of basic hair dye (França et al., 2015;Hehner et al., 2002;Indrawati et al., 2017). ...
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... Therefore, even if you've colored your hair before, it could be difficult to do so again without experiencing difficulties. Some hair colors can give sensitive people adverse reactions that result in skin discomfort and hair loss [12]. Before applying the color, the user must adhere to the user's instructions. ...
... Based on colored molecules, the first two dye classes (Table 1). Semi-permanent dyes can somewhat penetrate the hair cortex; therefore, the color permanence may resist up to six washes, in contrast to temporary dyes, which affect hair by accumulating on the cuticles [12]. ...
... A selection of anionic dyes with their structural and molecular formulations that are used in semi-permanent hair coloring. Adapted from ref [12]. ...
One of the oldest and most well-known cosmetics, hair color has been used by numerous ancient cultures throughout history on both men and women. It involves treating hair with various chemical compounds for changing hair color. According to how long they remain in the hair, these products are primarily divided into two categories: temporary and permanent. This classification is consistent with the types of active substances used in the dyeing process as well as the dyeing method itself, which are referred to as non-oxidative and oxidative hair dye products, respectively. Permanent hair dyes often consist of active chemicals that are not dyed but are oxidized to provide the desired color. As a result, the phrase "oxidative hair dye" was emerged. The precursor part and coupler part are the two main ingredients in formulations for oxidative hair dyes. Quinonediimine intermediates are momentary compounds that are generated when combined with hydrogen peroxide (developer). As a result, the coupler agent and these compounds interact to form the appropriate hair dye molecule. Notably, the entire dyeing process requires both an alkaline medium and an oxidizing agent, often hydrogen peroxide, to ensure that the staining agents reach the cuticle widely. This review's objective is to provide information about hair dye formulations and mechanisms of action as well as repairing damaged hair and new applications.
... Nowadays, regardless of economical and education backgrounds, millions of individuals worldwide commonly dye their hair to enhance youth and beauty and to follow fashion trends. Because hair colouration has become very popular, hair colouring products now represent one of the most rapidly growing beauty and personal care markets [1,2]. Regarding the year 2019, the global hair colour market was valued at approximately 22.2 billion USD, and it is expected to generate a revenue of around 37.4 billion USD by 2026 (Zion Market Research, NY, USA). ...
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... With the advancement of globalization, hair dye has become more and more popular among all cultures and ethnicities, desirable not only in natural colors but also in colors beyond individuals' genetic predispositions [1][2][3]. As a result, hair dyeing has become one of the most prosperous industries in cosmetics to date [4][5][6]. ...
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Confirmatory identification of hair colorants can be used to establish a connection between a suspect and the crime science or demonstrate the absence of such connections. A growing body of evidence shows that surface-enhanced Raman spectroscopy (SERS) could be a confirmatory, minimally destructive, and fully noninvasive analysis of hair colorants. In SERS, a signal that provide the information about the chemical structure of both permanent and semipermanent dyes present on hair is enhanced by a million-fold using noble metal nanostructures. However, it is unclear whether the information of hair colorants can be revealed if hair was contaminated or exposed to harsh environments such as sunlight and heat. In this work, we determine the effect of a short- and long-term heat exposure on SERS-based analysis of hair colored with blue and red permanent and semipermanent dyes. We found that short and especially long-term heat exposure at 220°C could alter chemical structure, and consequently SERS spectra, of permanent and semipermanent colorants. This thermal degradation of permanent dyes complicates their direct identification using SERS. We also found that partial least squares discriminant analysis can be used to overcome this issue allowing for highly accurate identification of both permanent and semipermanent dyes on colored hair that was exposed to 220°C for 6-12 min. These results show that heat exposure of colored hair should be strongly considered upon their SERS-based examination to avoid both false positive or false negative identification of chemical dyes.
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У статті розглянуто сучасні матеріали та технології, які впливають на конкретні образно‐іміджеві рішення колористичного дизайну зачіски. В основі розгляду колористичних дизайн‐технологій застосовано аналіз морфології та фізіології волосся, що виявляє функції цього природного елементу як специфічного матеріалу роботи дизайнера. Запропоновано методики діагностики його стану з метою прогнозування кінцевого результату дизайн‐проєкту. Наголошено, що до етапу первинної діагностики належить визначення вихідного кольору: природної або косметичної бази (РГТ, основний тон, відтінок, насиченість, рівномірність по довжині). Діагностика волосся дозволяє визначити стан структури волосся за низкою фізичних властивостей, таких як щільність, міцність, пористість, гігроскопічність, розтяжність, пружність, еластичність, кожна з яких впливає на процес фарбування волосся та кінцевий результат. Підсумовано, що з точки зору колористики діагностика є ключовим підходом у процесі створення кольорового рішення зачіски, досягнення результату дизайн-проєкту, в тому числі й зорового сприйняття. Виявлено логіку послідовності процедур з фарбування волосся, застосування сучасних матеріальних засобів для запобігання небажаного ефекту, забезпечення позитивного результату фарбування як шляху реалізації запроєктованого колористичного рішення за визначеним дизайном зачіски. Наголошено на важливості та обізнаності майстра в будові, фізичних та хімічних властивостях волосся як специфічного природного матеріалу, в тому числі його біосинтезу як фундаменту для практичного досягнення поставлених дизайнерських завдань. У результаті дослідження матеріалознавчої частини дизайну зачіски, а саме засобів для фарбування волосся, доведено, що цей процес є багатоетапним, складним і потребує професійних знань щодо якості всіх складників, детального розподілу технік та технологій у кожному конкретному випадку, а також врахування нюансів впливу на волосся парфумерно-косметичних препаратів як хімічних засобів отримання та збереження вибраного кольору. Для опрацювання письмових джерел та наукового фактажу матеріалознавства використано аналітичний підхід; для виявлення критеріїв розподілу сучасних засобів для зміни кольору волосся – типологічний; системний – для впорядкування різних даних, їх класифікації; компаративний – для порівняльного аналізу колористичних можливостей барвників, розмаїття способів їх використання, множини досягнення колористичних рішень як можливих варіантів дизайн-проєкту. Наукова новизна полягає в тому, що розглянуто морфологію та фізіологію волосся, його фізичні властивості у взаємодії з різними видами барвників та засобами знебарвлення. Виявлено риси спільності та відмінності у різних групах (класах) засобів по зміні кольору волосся, що має на меті визначати доцільність використання залежно від колористичних ідей, уникнути негативних наслідків хімічного впливу на структуру волосся, отримати намічені результати щодо колористичного плану. Такі класифікації узагальнено, систематизовано, представлено схематично.
In this thesis, the advanced spectroscopic techniques of atomic force microscopy - infrared (AFM-IR) spectroscopy and sum-frequency generation (SFG) spectroscopy are explored in detail for their innate ability to unravel the complexities of biological interfaces. The benefits of both techniques are demonstrated through applications to a variety of different interfaces, ranging from whole cells and aggregates (red blood cells and hair fibres) to artificial mimics (hydrogels) and thin molecular films (phospholipid monolayers). Specifically, the lateral chemical resolution and surface sensitivity of AFM-IR are used to chemically characterise the constituent components of biologically relevant systems below the diffraction limit whilst correlating these measurements to the nanoscale physical properties of the surface, such as topography, friction, and adhesion, that are accessible through traditional AFM. Similarly, the inherent surface specificity and sub-monolayer sensitivity of SFG is utilised, along with its ability to elucidate chemical structure and conformation, to probe oxidation in cell membranes, both in whole cells and monolayer mimics, thereby yielding a much deeper understanding of the oxidation mechanism due to reactive oxygen species (ROS) in physiological systems. Furthermore, some limitations and challenges associated with the use of these techniques in biologically relevant systems are identified, characterised and discussed, along with potential ways to circumvent them or minimise their impact in such investigations. Specifically, the inability of AFM-IR to probe thick substrates under aqueous conditions is discussed due to the relevance to studying many biological systems under physiological conditions. A novel method of sample preparation is proposed to maintain pseudo-aqueous conditions for the substrate whilst avoiding the limitations associated with AFM-IR measurement. Additionally, the common application of SFG to study surfactant monolayers at the air-water interface, particularly phospholipids due to them modelling cell membranes, is critically assessed for some inherent issues. The first example of which is associated with the inherent fluidity of the monolayer that makes it highly susceptible to local heating from the necessarily large incident fields. The effects of this local heating are thoroughly investigated and modelled, leading to conclusions about how to minimise this disruption in future investigations. Finally, SFG simulations are then used to quantitatively assess the validity of a common assumption associated with SFG investigations of phospholipids, namely that both alkyl chains yield the same spectral contributions despite having different orientational distributions.
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Almost all of the current hair dye products today contain synthetic chemicals which may cause allergic reactions in some users. Phycocyanin (PC), a non-toxic cyanobacterial pigment, has been used in the food and cosmetics sectors. There are however, been a few reports on the application of phycocyanin as a hair colorant. This study aimed to assess the biological qualities of phycocyanin for use in natural hair dye product. Phycocyanin was tested for use against anti skin-pathogen ( Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 14990, Methicillin-resistant Staphylococcus aureus (MRSA) DMST 20625, Propionibacterium acnes DMST 14916, Candida albicans DMST 21424, and Malassezia furfur M21), cytotoxicity of human immortalized keratinocyte (HaCaT) cells and tested for color fastness when used as a shampoo wash. According to the findings, Arthrospira (Spirulina) platensis phycocyanin has not shown the potential for use against anti-skin pathogenic microorganisms. While testing phycocyanin at the maximum doses of 2.5 mg/mL, the cytotoxicity test revealed that it is not hazardous to HaCaT cells. Bleached hair was dyed with a mixture of phycocyanin, natural developers, and mordants. A chroma meter was used to monitor color changes after shampoo washing. The findings revealed that phycocyanin has dyeability potential. 50% of the dyed hair color remained after 5 shampoo washes. The stability and color degradation of phycocyanin in hair dye powder formulation demonstrated good physical stability along with four cycles of heating/cooling. As a result, we can see that this pigment has the potential to be used as an active ingredient in natural hair dyes.
Synopsis--Data on patents for 33 primary intermediates and 20 color modifiers were collected from the literature. The effect of structure on shade, depth of color, light fastness, and solu-bility was determined for each product. The effect on color, depth of shade, and light fast-ness of dyeing mixtures of each of the 20 color modifiers with equimolar quantities of 3 pri-mary intermediates is reported. It is shown that by proper selection of color modifier the shade may be varied, the depth of color greatly increased, the fastness to light increased many fold, and the tendency to turn red on aging decreased. By using the formation of Bandrowski's base from oxidation of p-phenylenediamine as a tool the percentage of conversion to the colored form was shown to be only slightly more than 5% under the conditions normally used for dyeing hair. The effect of various factors on this yield is reported. The results of using five recently described pyridine derivatives are tabulated and dis-cussed.
Organic compounds present in plants have been used in various experimental conditions for dyeing tests aimed to develop safe and environmentally friendly temporary and semipermanent hair dyes. Yak hairs were used as a model for the colorimetric evaluation of red, yellow, blue, and brown shades conferred to hair by selected natural compounds. Two different sources for red, yellow, blue and brown shades were tested. Anthocyanins from mulberry fruits and alizarin emerged as promising candidates for red shades, anthocyanin-blue and curcumin for blue and yellow, respectively, and p-benzoquinone and juglone for browns. The influence of pH, dye concentration, soaking time, and medium in which the dyes have been dissolved or dispersed has been studied.
Human hair is the subject of a remarkably wide range of scientific investigations. Its chemical and physical properties are of importance to the cosmetics industry, forensic scientists and to biomedical researchers. The fifth edition of this book confirms its position as the definitive monograph on the subject. Previous editions were recognized as “concise and thorough” (Journal of the American Chemical Society), “an invaluable resource” (Canadian Forensic Science Society Journal), and “highly recommended” (Textile Research Journal). Chemical and Physical Behavior of Human Hair is a teaching guide and reference volume for cosmetic chemists and other scientists in the hair products industry, academic researchers studying hair and hair growth, textile scientists and forensic specialists. Features of the Fifth Edition: Recent advances in the classification and characterization of the different proteins and genes in IF and keratin associated proteins in human hair are described. The mechanism and incidence of hair growth and loss and hair density vs. age of males & females are described for Asians, Caucasians and Africans in different scalp regions. Details of hair surface lipids and cuticle membranes provide a better understanding of the surface and organization of the CMC and its involvement in stress strain is presented. Recent evidence demonstrates a more bilateral structure in curly hair and a more concentric arrangement of different cortical proteins in straighter hair. SNPs involved in hair form (curl and coarseness) and pigmentation and genes in alopecia and hair abnormalities are described. The latest biosynthetic scheme for hair pigments and structures for these and the different response of red versus brown-black pigments to photodegradation is described. A new method for curvature on 2,400 persons from different countries and groups is used to assign curvature throughout this book. Additional data for age and effects on diameter, ellipticity, elastic modulus, break stress and other parameters are presented with much larger data sets featuring statistical analyses. Hair conditioning, strength, breakage, split ends, flyaway, shine, combing ease, body, style retention, manageability and feel parameters are defined and described. A new section of different life stages by age groups considering collective and individual changes in hair fiber properties with age and how these affect assembly properties.
At present, the demand for hair color is rising globally. Because commercial hair colors have been reported to possess adverse effects on human health, their formulation is under strict regulation in each country. In this review, we briefly discuss the advantages and limitations of currently available chromatographic and electrophoretic methods, such as high performance liquid chromatography (HPLC), gas chromatography/gas chromatography with mass spectrometry (GC/GC-MS), and capillary electrophoresis (CE) employed for the analysis of dyestuffs present in commercial hair colors. Furthermore, a brief attempt has been made to classify hair colors according to their type and stability on hair. In addition, the chemistry behind dyeing is also briefly surveyed.
Synopsis Oxidation of hair fibers with diperisophthalic acid can produce extensive damage throughout several cuticle layers that is readily observed microscopically. At the same time, no detectable changes in the tensile properties (wet or dry) are detectable. These results are consistent with the hypothesis that the tensile properties of human hair are due primarily to the cortex, with little or no cuticle involvement. human hair. There is a long-standing hypothesis, that the cortex is primarily responsible for the tensile properties of human hair (1), although there is one publication with limited data suggesting the possibility of some cuticle involvement in the tensile properties of hair (2) and some evidence that wool fibers containing a medulla are weaker than non- medullated fibers (3). If the cortex is primarily responsible for the tensile properties of hair fibers, or even if there be only minor cuticle and/or medullary involvement in the tensile properties of hair, then the tensile properties are primarily an index of cortical damage. Therefore, if the tensile properties do not show change, without any further experimental evidence, such data does not stand as an indication of no hair damage. The lack of cuticle involvement in the tensile properties of hair or even minimal in- volvement might seem surprising, because, for a 70-micron hair fiber with a 4-micron- thick band of cuticular material (2), the cuticle represents approximately 22% of the total fiber cross-sectional area. Thus, it would be somewhat surprising if the cuticle were not involved at all in the tensile properties of human hair. With respect to medullary involvement in the tensile properties of hair, such involve- ment has only been demonstrated for selected wool fibers where the medulla represented more than 70 percent of the cross section (3), and such heavy medullation is not common in human hair. A few years ago, we examined an oxidative treatment for hair based on diperisophthalic acid. We found that under certain conditions this reagent could produce extensive
Synopsis--Proposals for the structure of Bandrowski's Base (BB) are reviewed, and it is concluded that the structure originally proposed by Green is the correct one. The role of BB in dyeing of human hair was studied by examining hair dyed with p-phenylenediamine and hydrogen peroxide. Solvent extraction of dyed hair or decomposition by dilute alkali yielded mixtures which contained little or no BB when they were examined by thin-layer chromatography. Based on these experiments, it is concluded that BB is not the main colorant of hair dyed with p-phenylenediamine.