Hair Semipermanent Dyes

Semipermanent hair dyes are designed for use on natural, unbleached hair to cover gray, add highlights, or rid hair of unwanted tones. Semipermanent dyes are longer-lasting than temporary dyes since they are retained in the hair shaft by weak polar and van der Waals attractive forces. A typical semipermanent dye will last through 6–10 shampooings. Usually, 10 to 12 dyes are mixed to obtain the desired shade, which must be darker than the natural hair color. Thus, in the cosmetic industry, semipermanent dyes are known as suitable for staying “on shade.” There are several different types of semipermanent hair dyes based on the derivation of the dye: textile dyes, vegetable dyes, and synthetic hair stains.

Semipermanent hair colorings derived from textile dyes are popular with both men and women. Since human hair is basically a textile, dyes for wool and natural fi ber cloths are well suited for adaptation to hair dyeing. The dyes used include the nitroanilines, nitrophenylenediamines, nitroaminophenols, azos, and anthraquinones. Sometimes these dyes are combined with henna, botanically known as Lawsonia alba, to create a “natural” vegetable dye. However, most of the currently marketed vegetable dyes use a small amount of synthetic henna, combined with traditional semipermanent dyes, to achieve the desired hair color. These dyes are commonly available as shampoos and mousses that are applied to wet, freshly shampooed hair and rinsed in 20 to 40 minutes.

A newer, longer-lasting form of the semipermanent dye, known as a demipermanent hair coloring, usually lasts through 10–12 shampooings. This is due to enhanced dye penetration into the hair shafts facilitated by the addition of small amounts of ammonia. As might be expected, demipermanent dyes are more damaging to the hair shafts than semipermanent dyes.

Hair Gradual Dyes

Gradual hair dyes, also known as metallic or progressive hair dyes, require repeated application to result in gradual darkening of the hair shaft. These products will change the hair color from gray to yellow-brown to black over a period of weeks. There is no control over the fi nal color of the hair, only the depth of color. The hair can only be darkened and not lightened with this technique. The most commonly used gradual hair dyes employ water-soluble lead salts, which are deposited on the hair shaft in the form of oxides, suboxides, and sulfides. The lead is in an inert form, thus gradual hair dyes pose no threat of lead poisoning.

This type of hair coloring is most popular among men who wish to blend their gray hair gradually over time with the surrounding darker hairs. Continued use is necessary to maintain the hair color. Gradual dyes cannot be combined with permanent waving or other hair-coloring techniques. The presence of the lead salts on the hair shaft creates unpredictable results if further chemical processing is undertaken. After prolonged use, gradual hair colorings may weaken the hair shaft and precipitate hair breakage.

Hair Rinses

Hair rinses are a special category of hair conditioners designed as thin liquids applied like an instant hair conditioner after shampooing and rinsed. They utilize cationic quaternary ammonium compounds, such as stearalkonium chloride and benzalkonium chloride. These products are mainly used to facilitate hair detangling by reducing friction and do little else to condition the hair shaft. They are intended for persons with oily hair who need little conditioning due to abundant sebum production.

Hair Leave-in Conditioners

Leave-in conditioners are applied following towel drying of the hair and are designed to remain on the hair shaft to aid in styling. They are removed with the next shampooing. A large category of leave-in conditioners, known as blow-drying lotions, are designed to coat the hair shaft and protect the hair protein from heat damage during the drying process.

The most popular leave-in hair conditioners are designed for persons with curly or kinky hair. These products lubricate and moisturize the hair shaft while aiding in styling. For example, oil sheen sprays and oily pomades help retain water within chemically straightened hair shafts and decrease the combing friction between hair shafts thereby preventing hair breakage. For persons with fine, straight hair, the oily leave-in conditioner would render the hair limp and hard to style, but for persons with coarse kinky hair, the oils improve manageability and impart shine. These products typically contain petrolatum, mineral oil, vegetable oils, and silicone and function as a true hair moisturizer.

Leave-in conditioners can create a film over the hair shaft that may be difficult to remove with shampooing. For individuals with tightly kinked hair, this is advantageous because it allows more frequent shampooing with less hair damage. Certainly for persons with fine, straight hair, this conditioner build-up would create the appearance of greasy, unclean hair. It is important to remember that the main purpose of a shampoo is to clean the scalp, not the hair. The amount and type of leave-in conditioner applied depends on degree of curl present in the hair shaft, tightly curled kinky hair requires more conditioning than straight hair.

Hair Instant Conditioners

Instant conditioners are aptly named, since they are applied directly from the bottle to the hair once it has been shampooed and rinsed. They are left in contact with the hair briefly for 1–5 minutes and then thoroughly rinsed. Due to their short contact time, they provide minimal conditioning and must be used after each shampooing to achieve the desired effect. The need for instant hair conditioners arose after hair shampoo detergents were developed with excellent sebum-removing capabilities. In addition, many of the currently popular hairstyles require frequent shampooing to remove styling gels, mousses, waxes, and sprays. Thus, the hair must be shampooed daily with a strong detergent leaving the hair unmanageable. Instant conditioners are used by persons who shampoo frequently and who have hair damaged by permanent waving or dyeing chemical processes.

Instant conditioners are the most popular type of hair conditioner for both home and salon use, even though they have limited ability to repair damaged hair. They contain water, conditioning agents, lipids, and thickeners. The conditioning agent usually consists of cationic detergent, known as quats.

Hair Shampoo Diversity

Even though all shampoos employ the same basic ingredients, the number of formulations on the market is diverse. This is because there are many different cleansing needs and hair types (Table 1). Shampoos designed for so-called normal hair thoroughly cleanse the scalp in persons with moderate sebum production and are best for chemically untreated hair. These shampoos are popular among men and use lauryl sulfate as the primary detergent, which provides good sebum removal and minimal conditioning. This is in contrast to dry-hair shampoos that provide mild cleansing and excellent conditioning. These products are excellent for mature hair, frequent use, and chemically treated hair since they reduce static electricity and increase manageability.

A relatively new shampoo category is the conditioning shampoo, also known as the 2-in-1 shampoo, which cleans and conditions simultaneously. Detergents used in conditioning shampoos are generally amphoterics and anionics of the sulfosuccinate type, previously discussed. These products are designed for patients with chemically damaged hair or those who prefer to shampoo frequently. Hydrolyzed animal protein is one of the ingredients added to conditioning shampoos, since it can minimally penetrate the hair shaft temporarily plugging surface defects, resulting in hair with a smoother feel and more shine. The protein can also temporarily mend split ends. Dimethicone is the other common conditioning shampoo ingredient prized for its ability to create a thin film over the hair shaft increasing shine and manageability.

For persons with abundant sebum production, oily-hair shampoos are formulated with excellent cleansing and minimal conditioning properties. These shampoos may use lauryl sulfate or sulfosuccinate detergents and are intended for adolescents or persons with extremely dirty hair. Products with this much detergency can be drying to the hair shaft if used daily in the absence of abundant sebum production.

The last major shampoo category contains products specifically designed for ethnic populations with tightly kinked hair. These shampoos are known as conditioning shampoos, since they are formulated with both cleaning and conditioning agents, such as wheat germ oil, steartrimonium hydrolyzed animal protein, lanolin derivatives, or dimethicone. Ethnic shampoos remove sebum from the hair shaft and replace it with a layer of oily conditioner to decrease kinky-hair combing friction. These shampoos are a variant of the 2-in-1 shampoos discussed earlier, since their main goal is to increase manageability and add shine. These shampoos are typically used weekly or once every two weeks. Many times an ethnic shampoo is used in conjunction with a conditioner, our next topic of discussion.

Hair Shampoo Formulation

Shampoos cleanse by utilizing synthetic detergents, also known as surfactants, which are amphiphilic. This means that the detergent molecule possesses both lipophilic, or oil-attracting, and hydrophilic, or water-attracting, sites. The lipophilic site binds to sebum and oil-soluble dirt while the hydrophilic site binds to water allowing removal of the sebum with water rinsing. There are four basic categories of shampoo detergents: anionics, cationics, amphoterics, and nonionics. Usually, a shampoo is a combination of two to four detergents with various abilities to remove sebum, produce foam, and condition the hair. Creating the perfect balance between hygiene and beautification is the goal of a successful shampoo.

Anionic detergents are the most popular cleanser in general purpose shampoos and are named for their negatively charged hydrophilic polar group. Anionic detergents are adept at removing sebum from the scalp, but leave the hair harsh, rough, subject to static electricity, dull, and difficult to detangle. Common anionic detergents include the lauryl sulfates, laureth sulfates, sarcosines, and sulfosuccinates. The second most popular detergents are the amphoterics, which contain both an anionic and a cationic group. This allows them to behave as cationic detergents at low pH and as anionic detergents at high pH. Within the amphoteric detergent category, there are several subgroups, which include the betaines, sultaines, and imidazolinium derivatives. Amphoteric detergents such as cocamidopropyl betaine and sodium lauraminopropionate are found in baby shampoos. These detergents actually numb the tissues of the eyes, which accounts for the non-stinging characteristics of baby shampoo. Amphoteric detergents are also used in shampoos for fine and chemically treated hair because they foam moderately well while leaving the hair manageable.

The main distinguishing characteristic between a bar cleanser and a shampoo is the addition of a sequestering agent. Sequestering agents function to chelate magnesium and calcium ions thereby preventing the formation of insoluble soaps, known as scum. Without sequestering agents, shampoos would leave a film on the hair, making it appear dull.