caress
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from http://www.emedicine.com:
HAIR CLEANSING
Hair cleansing is a more complex interaction than skin cleansing, since the surface to cleanse is much greater, consisting of the scalp and all surfaces of each hair shaft. Products designed to cleanse the hair are known as shampoos.
Formulation
Shampoos basically contain detergents, foaming agents, conditioners, thickeners, opacifiers, softeners, sequestering agents, fragrances, preservatives, and specialty additives. Detergents are the primary sebum and dirt removal shampoo components; however, excessive removal of sebum leaves the hair dull, susceptible to static electricity, and difficult to comb. Furthermore, consumers equate cleansing ability with abundant, long-lasting foam. Excessive bubbles are not a technical requirement for good hair cleansing and bacteria removal, but shampoo manufacturers add increased amounts of detergents, in addition to foam boosters, to obtain the foam that is desired by consumers. This increased concentration of detergent creates the need for conditioners and other additives in shampoos to improve their cosmetic acceptability.
Detergents
Shampoos function by employing detergents (also known as surfactants) that are both lipophilic (oil-loving) and hydrophilic (water-loving). The lipophilic component adheres to sebum and the hydrophilic component allows water to rinse away the sebum.
Some of the most common synthetic detergents combined into various shampoo formulations for various needs are as follows:
* Lauryl sulfates (sodium lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate) are found in most shampoos as the main surfactant since they work well in both hard and soft water, produce rich foam, and are easy to remove. This group produces good cleansing but is hard on the hair.
* Laureth sulfates (sodium laureth sulfate, triethanolamine laureth sulfate, ammonium laureth sulfate) produce rich foam, provide good cleansing, and leave hair in good condition. They also are a common main surfactant.
* Sarcosines (lauryl sarcosine, sodium lauryl sarcosinate) are poor cleansers but are excellent conditioners. This group commonly is used as a secondary surfactant.
* Sulfosuccinates (disodium oleamine sulfosuccinate, sodium dioctyl sulfosuccinate) are strong degreasers and commonly are used as a secondary surfactant in oily hair shampoos.
The aforementioned detergents are classified as anionic surfactants because of their negatively charged hydrophilic polar group. Another group of detergents, the cationic detergents, is named for their positively charged polar group. They are relatively poor detergents and do not lather well, but their unpopularity is largely due to their incompatibility with other anionic surfactants. Some shampoos designed for dyed or bleached hair use cationic detergents because they are excellent at imparting softness and manageability.
The nonionic detergents, the second most popular group of detergents behind the anionic surfactants, possess no polar group. These are the mildest of all surfactants and are used in combination with anionic surfactants as a secondary cleanser. Examples include polyoxyethylene fatty alcohols, polyoxyethylene sorbitol esters, and alkanolamides.
The amphoteric detergents contain both an anionic and a cationic group so that they behave as cationics at lower pH values and anionics at higher pH values. The detergents that fall within this group are the betaines, sultaines, and imidazolinium derivatives. Such ingredients as cocamidopropyl betaine and sodium lauraminopropionate are found in baby shampoos, since they are nonirritating to the eyes. These surfactants foam moderately well and leave the hair manageable, making them a good choice for chemically treated and fine hair.
Foaming agents
Foaming agents in shampoos introduce gas bubbles into the water. Many consumers believe that shampoos that generate copious foam are better cleansers than poorly foaming shampoos. This is not true. As the shampoo removes sebum from the hair, the amount of foam will decrease because sebum inhibits bubble formation. This accounts for the increased foam seen on the second shampooing, when most of the sebum has been removed.
Thickeners and opacifiers
Thickeners and opacifiers have no part in hair cleansing. They simply make the product more appealing to the consumer. Many people incorrectly believe that a thick shampoo is more concentrated than a thin shampoo; others want a shampoo that appears opaque or pearlescent.
Conditioners
Conditioners impart manageability, gloss, and antistatic properties to the hair. They are found in most shampoos for dry, damaged, or treated hair. They usually are fatty alcohols, fatty esters, vegetable oils, mineral oils, or humectants. Many conditioners are used in dry hair shampoos, including hydrolyzed animal protein, glycerin, dimethicone, simethicone, polyvinylpyrrolidone, propylene glycol, and stearalkonium chloride.
Sequestering agents
Sequestering agents make shampoos function better than bar soaps in cleansing the hair. They chelate magnesium and calcium ions so that other salts or insoluble soaps, known as scum, are not formed. Without sequestering agents, shampoos would leave a film on the hair.
pH adjusters
Some shampoos contain ingredients designed to alter pH, allowing the marketing claim of "pH balanced." Most shampoos are alkaline, which can swell the hair shaft and render it more susceptible to damage. This is not a problem for patients with healthy, nonporous hair containing an intact cuticle. Patients with damaged or chemically treated hair with a fragmented cuticle may wish to avoid hair swelling by selecting a shampoo that has an acid added to balance the pH.
Specialty additives
The key differences between similar purpose shampoos manufactured by various personal care product companies are the fragrance and special care additives. Such additives as wheat germ oil (containing vitamin E) and panthenol (a form of vitamin B) are added mainly because they are believed to leave hair more silky and manageable. Other producers add fatty substances, such as plant extracts or mink oil. Proteins, such as ribonucleic acid, collagen, and placenta, may be added to act as conditioners. Some shampoos now include a chemical sunscreen.
Types of shampoo
Shampoos have been formulated in liquids, gels, creams, aerosols, and powders. Only the liquids are discussed in this article because they are the most popular. A number of different types of shampoos also are available, including basic shampoos (normal, dry, oily, and chemically treated hair shampoos), baby shampoos, conditioning shampoos, medicated shampoos, and professional shampoos.
Basic shampoos
Basic shampoos may be selected from several formulations depending on the amount of scalp sebum production, hair shaft diameter, and hair shaft condition. The label usually defines the intended consumer by stating normal hair, oily hair, dry hair, or damaged, colored-treated hair. Some companies alter the concentrations of detergents and conditioners to make different formulations, but the ingredient lists may be identical for all formulations. Other product lines have different formulations for each type.
Normal hair shampoos use lauryl sulfate detergents, giving them good cleansing and minimal conditioning characteristics. These products work well for adults with moderate sebum production and coarse hair; however, they do not work well for persons with fine, unmanageable hair.
Oily hair shampoos have excellent cleansing and minimal conditioning properties. They may use lauryl sulfate or sulfosuccinate detergents and are intended for adolescents with oily hair or persons who have extremely dirty hair. They can be drying to the hair shaft if used daily. Following an oily hair shampoo with use of a heavy conditioner is self-defeating.
Dry hair shampoos provide mild cleansing and good conditioning. Some companies recommend the same product for dry hair and damaged hair. These products are excellent for mature persons and those who wish to shampoo daily. They reduce static electricity and increase manageability in fine hair; however, some products provide too much conditioning, which may result in limp hair. Dry hair shampoos also may cleanse so poorly that conditioner can build up on the hair shaft. This condition has been labeled as the "greasies" in popular advertising and may account for the observation that hair sometimes has more body after using a different shampoo.
Damaged hair shampoos are intended for hair that has been chemically treated with permanent hair colors, hair bleaching agents, permanent waving solutions, or hair straighteners. Hair also can be damaged physically by over cleansing, excessive use of heated styling devices, and vigorous brushing or combing. Longer hair is more likely to be damaged than shorter hair since it undergoes a natural process known as weathering, whereby the cuticular scales are decreased in number from the proximal to distal hair shaft. As mentioned previously, damaged hair shampoos may be identical to dry hair shampoos or may contain mild detergents and increased conditioners. Hydrolyzed animal protein is the superior conditioner for damaged hair since it can minimally penetrate the shaft and temporarily plugging surface defects, resulting in hair with a smoother feel and more shine. It is important that the protein is hydrolyzed; larger protein molecules cannot penetrate the hair shaft.
Baby shampoos
Baby shampoos are nonirritating to the eyes and designed as mild cleansing agents since babies produce limited sebum. These shampoos use detergents from the amphoteric group. Baby shampoos also are appropriate for mature hair and for individuals who wish to shampoo daily.
Conditioning shampoos
Conditioning shampoos may be labeled as such or may be labeled as shampoos for dry or damaged hair. Detergents used in conditioning shampoos generally are amphoterics and anionics of the sulfosuccinate type. These products sometimes are known as one-step shampoos, since a conditioner need not be applied following shampooing.
Medicated shampoos
Medicated shampoos, also known as dandruff shampoos, contain additives, such as tar derivatives, salicylic acid, sulfur, selenium disulfide, polyvinylpyrrolidone-iodine complex, chlorinated phenols, or zinc pyrithione. Medicated shampoos have several functions that include the following: to remove sebum efficiently, to remove scalp scale, to decrease scalp scale production, and to act as an antibacterial/antifungal. The shampoo base removes sebum, while mechanical scrubbing removes scalp scale. Tar derivatives commonly are used as anti-inflammatory agents. Sulfur and zinc pyrithione are used for their antibacterial/antifungal qualities. Menthol is added to some shampoos to produce a tingling sensation that some patients find esthetically pleasing.
Adverse reactions
Shampoos do not represent a common cause of cutaneous irritant or allergic contact dermatitis because of their relatively brief contact with the skin prior to rinsing. However, eye irritation can be a problem, which some shampoos overcome with the addition of imidazoline-type amphoteric surfactants, succinic ester sulfonates, silicone glycols, and fatty acid-peptide condensates. Ingredients in shampoos that are possible sensitizers include formalin, parabens, hexachlorophene, fragrances, triclosan, and miranols.
Shampoos should be diluted to form a 1-2% aqueous solution for closed patch testing and a 5% aqueous solution for open patch testing. However, false-positive reactions due to irritation still may occur. A better assessment may be obtained by patch testing individual ingredients separately.
HAIR CLEANSING
Hair cleansing is a more complex interaction than skin cleansing, since the surface to cleanse is much greater, consisting of the scalp and all surfaces of each hair shaft. Products designed to cleanse the hair are known as shampoos.
Formulation
Shampoos basically contain detergents, foaming agents, conditioners, thickeners, opacifiers, softeners, sequestering agents, fragrances, preservatives, and specialty additives. Detergents are the primary sebum and dirt removal shampoo components; however, excessive removal of sebum leaves the hair dull, susceptible to static electricity, and difficult to comb. Furthermore, consumers equate cleansing ability with abundant, long-lasting foam. Excessive bubbles are not a technical requirement for good hair cleansing and bacteria removal, but shampoo manufacturers add increased amounts of detergents, in addition to foam boosters, to obtain the foam that is desired by consumers. This increased concentration of detergent creates the need for conditioners and other additives in shampoos to improve their cosmetic acceptability.
Detergents
Shampoos function by employing detergents (also known as surfactants) that are both lipophilic (oil-loving) and hydrophilic (water-loving). The lipophilic component adheres to sebum and the hydrophilic component allows water to rinse away the sebum.
Some of the most common synthetic detergents combined into various shampoo formulations for various needs are as follows:
* Lauryl sulfates (sodium lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate) are found in most shampoos as the main surfactant since they work well in both hard and soft water, produce rich foam, and are easy to remove. This group produces good cleansing but is hard on the hair.
* Laureth sulfates (sodium laureth sulfate, triethanolamine laureth sulfate, ammonium laureth sulfate) produce rich foam, provide good cleansing, and leave hair in good condition. They also are a common main surfactant.
* Sarcosines (lauryl sarcosine, sodium lauryl sarcosinate) are poor cleansers but are excellent conditioners. This group commonly is used as a secondary surfactant.
* Sulfosuccinates (disodium oleamine sulfosuccinate, sodium dioctyl sulfosuccinate) are strong degreasers and commonly are used as a secondary surfactant in oily hair shampoos.
The aforementioned detergents are classified as anionic surfactants because of their negatively charged hydrophilic polar group. Another group of detergents, the cationic detergents, is named for their positively charged polar group. They are relatively poor detergents and do not lather well, but their unpopularity is largely due to their incompatibility with other anionic surfactants. Some shampoos designed for dyed or bleached hair use cationic detergents because they are excellent at imparting softness and manageability.
The nonionic detergents, the second most popular group of detergents behind the anionic surfactants, possess no polar group. These are the mildest of all surfactants and are used in combination with anionic surfactants as a secondary cleanser. Examples include polyoxyethylene fatty alcohols, polyoxyethylene sorbitol esters, and alkanolamides.
The amphoteric detergents contain both an anionic and a cationic group so that they behave as cationics at lower pH values and anionics at higher pH values. The detergents that fall within this group are the betaines, sultaines, and imidazolinium derivatives. Such ingredients as cocamidopropyl betaine and sodium lauraminopropionate are found in baby shampoos, since they are nonirritating to the eyes. These surfactants foam moderately well and leave the hair manageable, making them a good choice for chemically treated and fine hair.
Foaming agents
Foaming agents in shampoos introduce gas bubbles into the water. Many consumers believe that shampoos that generate copious foam are better cleansers than poorly foaming shampoos. This is not true. As the shampoo removes sebum from the hair, the amount of foam will decrease because sebum inhibits bubble formation. This accounts for the increased foam seen on the second shampooing, when most of the sebum has been removed.
Thickeners and opacifiers
Thickeners and opacifiers have no part in hair cleansing. They simply make the product more appealing to the consumer. Many people incorrectly believe that a thick shampoo is more concentrated than a thin shampoo; others want a shampoo that appears opaque or pearlescent.
Conditioners
Conditioners impart manageability, gloss, and antistatic properties to the hair. They are found in most shampoos for dry, damaged, or treated hair. They usually are fatty alcohols, fatty esters, vegetable oils, mineral oils, or humectants. Many conditioners are used in dry hair shampoos, including hydrolyzed animal protein, glycerin, dimethicone, simethicone, polyvinylpyrrolidone, propylene glycol, and stearalkonium chloride.
Sequestering agents
Sequestering agents make shampoos function better than bar soaps in cleansing the hair. They chelate magnesium and calcium ions so that other salts or insoluble soaps, known as scum, are not formed. Without sequestering agents, shampoos would leave a film on the hair.
pH adjusters
Some shampoos contain ingredients designed to alter pH, allowing the marketing claim of "pH balanced." Most shampoos are alkaline, which can swell the hair shaft and render it more susceptible to damage. This is not a problem for patients with healthy, nonporous hair containing an intact cuticle. Patients with damaged or chemically treated hair with a fragmented cuticle may wish to avoid hair swelling by selecting a shampoo that has an acid added to balance the pH.
Specialty additives
The key differences between similar purpose shampoos manufactured by various personal care product companies are the fragrance and special care additives. Such additives as wheat germ oil (containing vitamin E) and panthenol (a form of vitamin B) are added mainly because they are believed to leave hair more silky and manageable. Other producers add fatty substances, such as plant extracts or mink oil. Proteins, such as ribonucleic acid, collagen, and placenta, may be added to act as conditioners. Some shampoos now include a chemical sunscreen.
Types of shampoo
Shampoos have been formulated in liquids, gels, creams, aerosols, and powders. Only the liquids are discussed in this article because they are the most popular. A number of different types of shampoos also are available, including basic shampoos (normal, dry, oily, and chemically treated hair shampoos), baby shampoos, conditioning shampoos, medicated shampoos, and professional shampoos.
Basic shampoos
Basic shampoos may be selected from several formulations depending on the amount of scalp sebum production, hair shaft diameter, and hair shaft condition. The label usually defines the intended consumer by stating normal hair, oily hair, dry hair, or damaged, colored-treated hair. Some companies alter the concentrations of detergents and conditioners to make different formulations, but the ingredient lists may be identical for all formulations. Other product lines have different formulations for each type.
Normal hair shampoos use lauryl sulfate detergents, giving them good cleansing and minimal conditioning characteristics. These products work well for adults with moderate sebum production and coarse hair; however, they do not work well for persons with fine, unmanageable hair.
Oily hair shampoos have excellent cleansing and minimal conditioning properties. They may use lauryl sulfate or sulfosuccinate detergents and are intended for adolescents with oily hair or persons who have extremely dirty hair. They can be drying to the hair shaft if used daily. Following an oily hair shampoo with use of a heavy conditioner is self-defeating.
Dry hair shampoos provide mild cleansing and good conditioning. Some companies recommend the same product for dry hair and damaged hair. These products are excellent for mature persons and those who wish to shampoo daily. They reduce static electricity and increase manageability in fine hair; however, some products provide too much conditioning, which may result in limp hair. Dry hair shampoos also may cleanse so poorly that conditioner can build up on the hair shaft. This condition has been labeled as the "greasies" in popular advertising and may account for the observation that hair sometimes has more body after using a different shampoo.
Damaged hair shampoos are intended for hair that has been chemically treated with permanent hair colors, hair bleaching agents, permanent waving solutions, or hair straighteners. Hair also can be damaged physically by over cleansing, excessive use of heated styling devices, and vigorous brushing or combing. Longer hair is more likely to be damaged than shorter hair since it undergoes a natural process known as weathering, whereby the cuticular scales are decreased in number from the proximal to distal hair shaft. As mentioned previously, damaged hair shampoos may be identical to dry hair shampoos or may contain mild detergents and increased conditioners. Hydrolyzed animal protein is the superior conditioner for damaged hair since it can minimally penetrate the shaft and temporarily plugging surface defects, resulting in hair with a smoother feel and more shine. It is important that the protein is hydrolyzed; larger protein molecules cannot penetrate the hair shaft.
Baby shampoos
Baby shampoos are nonirritating to the eyes and designed as mild cleansing agents since babies produce limited sebum. These shampoos use detergents from the amphoteric group. Baby shampoos also are appropriate for mature hair and for individuals who wish to shampoo daily.
Conditioning shampoos
Conditioning shampoos may be labeled as such or may be labeled as shampoos for dry or damaged hair. Detergents used in conditioning shampoos generally are amphoterics and anionics of the sulfosuccinate type. These products sometimes are known as one-step shampoos, since a conditioner need not be applied following shampooing.
Medicated shampoos
Medicated shampoos, also known as dandruff shampoos, contain additives, such as tar derivatives, salicylic acid, sulfur, selenium disulfide, polyvinylpyrrolidone-iodine complex, chlorinated phenols, or zinc pyrithione. Medicated shampoos have several functions that include the following: to remove sebum efficiently, to remove scalp scale, to decrease scalp scale production, and to act as an antibacterial/antifungal. The shampoo base removes sebum, while mechanical scrubbing removes scalp scale. Tar derivatives commonly are used as anti-inflammatory agents. Sulfur and zinc pyrithione are used for their antibacterial/antifungal qualities. Menthol is added to some shampoos to produce a tingling sensation that some patients find esthetically pleasing.
Adverse reactions
Shampoos do not represent a common cause of cutaneous irritant or allergic contact dermatitis because of their relatively brief contact with the skin prior to rinsing. However, eye irritation can be a problem, which some shampoos overcome with the addition of imidazoline-type amphoteric surfactants, succinic ester sulfonates, silicone glycols, and fatty acid-peptide condensates. Ingredients in shampoos that are possible sensitizers include formalin, parabens, hexachlorophene, fragrances, triclosan, and miranols.
Shampoos should be diluted to form a 1-2% aqueous solution for closed patch testing and a 5% aqueous solution for open patch testing. However, false-positive reactions due to irritation still may occur. A better assessment may be obtained by patch testing individual ingredients separately.
