Coloring hair

Darkening the natural color of the hair can be accomplished through the action of temporary dyes that act similarly to a hair conditioner. Most temporary chemical dyes contain the salts of large acidic molecules (e.g., FD C Blue No. I) that do not easily penetrate the hair outer cuticle. A colored film forms over each hair and washes off with the action of a 

Permanent hair dyes are often derivatives of an aromatic amine, discovered as a hair dye in 1883, called /Mra-phenylenediamine (H2N-C6H4-NH2), including primary intermediates such as pcirci-aminophenol, dihydroxybenzene, 4-methylaminophenol, tetraaminopyrimidine, 2-aminomethyl-4-aminophenol, and / ara-aminodiphenylamine. The / zrra-phenylenedi-amine compound produces a black color, with its derivative parci- mmo-diphenylaminesulfonic acid used in blond formulations. Couplers are generally aromatic phenols or amines that have an available site that is subject to electrophilic interaction. Typical couplers include chemicals such as resorcinol, wrte-phenylenediamine, 2,4-diaminoanisole, mrm-aminophenol, 

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Chemistry produces many materials, other than drugs, that have to be optimized in their properties and preparation. Chemoinformatics methods will be used more and more for the elucidation and modeling of the relationships between chemical structure, or chemical composition, and many physical and chemical properties, be they nonlinear optical properties, adhesive power, conversion of light into electrical energy, detergent properties, hair-coloring suitabHty, or whatever. 

Moreover, multivariate optimization, the simultaneous optimization of several properties, will increasingly come into focus. A drug should have high selectivity in binding to different receptors and minimal toxicity, good solubility and penetration, and so on. A hair color should have a brilliant shine, be absorbed well, not be washed out, not damage the hair, not be toxic, and be stable under sunlight, etc. 

Hair products are normally cosmetics and are thus subject to aU. laws and regulations that control the labeling and claims of aU. cosmetic products. There are, however, several significant variations to this premise, ie, hair colorants, professional use only products, and products that make dmg claims. 

Hair coloring preparations have been in use since the ancient Egyptians, and recorded recipes exist in many cultures. These followed the traditional apphcation of plant extracts or metallic dyes, both of which still are used. In the latter part of the nineteenth century, synthetic organic compounds were discovered which eventually led to modem hair coloring. 

Modem hair colorants can be divided into temporary, semipermanent, and permanent systems. These categories are characterized by the durabiUty of the color imparted to the hair, the type of dye employed, and the method of apphcation (see Dyes and dye intermediates). 

There is a wide variety of dyes unique to the field of hair coloring. Successive N-alkylation of the nitrophenylenediamines has an additive bathochromic effect on the visible absorption to the extent that violet-blue dyes can be formed. Since the simple A/-alkyl derivatives do not have good dyeing properties, patent activity has concentrated on the superior A/-hydroxyalkyl derivatives of nitrophenylenediamines (29,30), some of which have commercial use (31). Other substituents have been used (32). A series of patents also have been issued on substituted water-soluble azo and anthraquinone dyes bearing quaternary ammonium groups (33). 

Semipermanent hair color products are formulated at an alkaline pH, usually between 8.5 and 10. At this pH the cuticle of the hair lifts away from the hair a Httie, allowing for easier penetration of dye. An alkyl amine buffered with an organic acid normally is used to obtain the desired pH. The formulations contain a mixture of solvents and surfactants to solubilize the dyes and a thickening agent is added so that the product stays on the hair without mnning or dripping. A 20—30 min appHcation time is normal for this type of product. A representative formula for a semipermanent dye product is given in Table 7. 

Semipermanent hair color products have the advantage of being removable if a consumer is not satisfied with the result, the color is gradually washed out of the hair. The products are perceived as very gentie. The ease of removal of these products is also a disadvantage because a consumer needs to reapply the color after every 6—8 shampoos to maintain the color. 

Permanent Hair Colorants. Permanent colorants produce hair coloration that lasts until the hair grows out. Color is formed inside the hair by hydrogen peroxide-induced coupling reactions of colorless dye precursors. A hiU range of shades can be obtained with this system and the permanent or oxidative hair colorants are considered to be the most important class of hair dyes. 

Also present but not essential in permanent hair colorants are nitro dyes which dye hair without oxidation. These dyes, nitro derivatives of aminophenols and benzenediamines, impart yellow, orange, or red tones. Although they have good tinctorial value, they are not as colorfast as the oxidative dyes. They also are used in semipermanent hair colorants. 

Table 8. Permanent Hair Colorant Formulation for a Medium Brown Shade...

After the hair is bleached it has an uimatural straw-like color and is then dyed to the desired tone with either a semipermanent or a permanent hair color product. The dye products designed to color bleached hair to a natural looking blonde shade are called toners. 

The presence of ammonia and hydrogen peroxide in permanent hair color products is a disadvantage. Both are considered by consumers to be harsh chemicals. The odor of ammonia is unpleasant for a personal care product. Monoethanol amine has been used as a substitute for ammonia in some commercial permanent hair color products. It is not as effective as ammonia in allowing the hair to be lightened but it does not have as strong an odor. 

Melanin Drying. One development (ca 1993) in hair coloring involves the formation of pigments within the hair that are very similar to natural melanin. Thus either catalytic or air oxidation of 5,6-dihydroxyindole [3131-52-0] can be effectively used to permanently dye hair within a short time (38). The formed color can, if required, be further modulated with dilute H2O2 or can be even totally removed from hair by this oxidant. 

Metallic Dyes. MetaUic dyes are among the older hair color materials known. Commercial products are based on a 1% solution of lead acetate in an aqueous, slightly acidic, alcohoHc medium. Precipitated sulfur appears to be essential. The convenience aspect is stressed by the leave-in appHcation method. Actually, the color development is so slow, taking about a week to ten days, that there is no alternative to this technique. Daily appHcation is needed at first. 

Hair Coloring Regulation Issues. In the United States the classification of color additives is complex. Under the Federal Food, Dmg and Cosmetic Act, all cosmetic colors must be the subject of an approved color additive petition to the Food and Dmg Administration there is an exception for coal-tar colorants used to color hair. Based on the composition of these colorants, FDA can require a certification on each manufactured batch of colorant to assure conformance with the approved specifications. In the early 1990s FDA has required certification only for synthetically derived coal-tar type colors. Many of the approved color additives, both certified and noncertified, are restricted ia their potential use. These restrictions can be found ia the color additive regulations ia the Code of Federal Regulations at 21 CFR 73 and 74. 

Many products in the hair care and hair color categories are distributed solely for professional use by cosmetologists, beauticians, and hairdressers in their places of business. 

Amin ophen o1 has been used as a stabilizer of chlorine-containing thermoplastics (153), although its principal use is as an intermediate in the production of 4-aniino-2-hydroxybenzoic acid [65-49-6] a tuberculostat. This isomer is also employed as a hair colorant and as a coupler molecule in hair dyes (154,155). 

Hair colorants, the fourth class of color additives, may be used only to color scalp hair and may not be used in the area of the eye. Use of these colorants is exempt, that is, coal-tar hair dyes may be sold with cautionary labeling, directions for preliminary (patch) testing, and restrictions against use in or near the eye. The EDA diligently enforces the rules governing color additives and limits the use of, or even dehsts colorants deemed unsafe. The Hst of substances specifically prohibited for use in cosmetics is short. 

Performance. Consumer acceptance is a criterion on which cosmetic marketers caimot compromise. Whereas the likes and dislikes of consumers are in a state of constant flux, some product features are critical. A deodorant that does not deodorize or a hair coloring that fades in sunlight is unacceptable. Performance is tested by in vitro techniques during formulation, but the ultimate test of a product s performance requires in-use experience with consumers and critical assessment by trained observers. Performance tests can sometimes be combined with in-use safety tests, and protocols for such programs have been developed. 

Hair Colorants. Hair colorants are commonly divided into temporary, semipermanent, and permanent types. Decolorizing (bleaching) represents a fourth type of hair coloring (81) (see Bleaching agents). 

Temporary hair colorants are removed from the hair by a single shampoo. Temporary hair colorants usually employ certified dyes that have tittle affinity for hair (see Table 9). They are incorporated into aqueous solutions, shampoos, or hair-setting products. 

In hair coloring a light ash blond shade may require as Httie as 0.5—1% of intermediates, whereas a tme black may require up to about 5%. In principle, the formulator blends precursors that yield red, blue, and yellow dyes. The base in which the components are dissolved or suspended is similar to that used in simple bleaches and may include alkanolamides, various types of surfactants, thickening agents, and solvents. Removal of undesirable dyes is achieved by treating the discolored hair with a powerful reductant of the sulfite family. 

Alternatively, the metathesis can be effected by sulfites or bisulfites that convert cystine iato one cysteiae residue and one thiosulfate (Bunte salt) residue. Hair waving based on sulfites is slower than that based on mercaptans and is more likely to cause changes ia hair color. 

Compositions have been pubHshed for cream tinses (82), hair conditioners, dressiags, and mousses (83), hair-styling products (84), hair sprays (85), hair colorants (86), hair-waving products (87), hair-straightening products (88), and depilatories (89). 

In the United States the use of coal-tar dyes ia eye makeup is geaerally prohibited. The use of permanent and temporary hair colorants (Tables 16 and 17) and of organic dyes and their lakes is precluded. As a result, only iasoluble inorganic pigments can be used (Table 9). The sensitivity of the eye... 

Symptoms of molybdenum poisoning in cattle include emaciation, diarrhea, anemia, stiffness, and fading of hair color. Vegetation containing 230 mg/kg of this substance affects cattle. 

Rosacea is a chronic disorder affecting the central parts of the face, characterized by flushing, persistent erythema and teleangectasia. Inflammatory papules and pustules can develop within the areas of erythema. Rosacea typically occurs in adults with fair skin and light eye and hair color. In contrast to acne, rosacea is not typically follicular in nature and comedones and seborrhea are usually absent. Pyoderma fa-dale is deemed to be an explosive form of rosacea, often occurring in young women with a phenotype typical of rosacea patients, often in the context of stress (Fig. 11.16). 

Normal hair is slightly acidic. In fact, the pH of hair is between 4.5 and 5.5. Hair that becomes too alkaline dries out, tangles easily, becomes dull, and generally looks damaged. Chemical processes, such as permanent waves, hair coloring, and bleaching, as well as a person s natural body chemistry, can all raise the hair s pH. 

In the home, you or your children may be exposed to lead if you take some types of home remedy medicines that contain lead compounds. Lead compounds are in some non-Westem cosmetics, such as surma and kohl. Some types of hair colorants and dyes contain lead acetate. Read the labels on hair coloring products, use them with caution, and keep them away from children. 

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