Shampoo: Encyclopedia - Shampoo

Shampoo

Shampoo is a hair care product primarily used to remove the oils, dirt, skin particles and grime that gradually build-up in the hair.

Shampoo - History

The word shampoo in English usage dates back to 1762, with the meaning "to massage". The word was a loan from Anglo-Indian shampoo, in turn from Hindi champo, imperative of champna, "to press, knead the muscles, massage".

During the early stages of shampoo, English hairdressers boiled soap in soda water and added herbs to give the hair health and fragrance.

Originally soap and shampoo were very similar products; both were often made from surfactants, a type of detergent. Shampoo became the logical evolution of personal hygiene products, and targeted the specific needs of hair and not the body in general. Through out the course of the 20th century a number of specifically designed shampoos were released that gently and effectively cleaned a variety of different hair types. Now, synthetic surfactants are primarily used in shampoo.

Hair conditioner is often applied after shampooing to improve the texture and appearance of hair.

Shampoo - Description

Shampoos are used to clean hair by stripping sebum from the hair. Sebum is naturally occurring oil that coats the hair and tends to collect dirt, styling products and scalp flakes. Surfactants clean hair by stripping sebum from hair shafts therefore removing the dirt attached to it.

While both soaps and shampoos contain the cleaning agent surfactants, soap is specifically designed to clean the body and might be too harsh on hair.

The difference between shampoo and soap include:

• Proper detergency without degreasing
• Ability to form delicate and rich bubbling
• Easy rinsing
• Good finish after washing hair
• Minimal skin/eye irritation
• No damage to hair
• Low toxicity
• Good biodegradability

The chemical mechanisms that underly hair cleansing are complex. Undamaged hair has a hydrophobic surface to which skin lipids are strongly adsorbed. The skin lipids (sebum) are so strongly attached to hair that they will not come off with plain water. When shampoo is applied to wet hair, the anionic surfactants are adsorbed onto the hair shaft by their hydrophobic tails and the negatively charged heads orientate outwards. The hair fiber's surface is then wetted by water that has had its interfacial tension reduced by the surfactants. This displaces any non-polar materials (oil, grease) that are attached to the hair shaft. The semi-polar oily materials also on the hair shaft are solubilised into the surfactant micelle structures of the shampoo and are removed by rinsing. Particulate matter adheres to hair primarily due to adhering to the oily surface, and are easily removed by rinsing once the oil is solubilised into the shampoo.

Shampoo - Ingredients

Shampoo - Detergents

Surfactants, also known as wetting agents, lower the surface tension of a liquid, allowing easier spreading, and the interfacial tension between two liquids. The term surfactant is a contraction of "Surface active agent".

The major types of surfactants are used in shampoos include:

• Anionic (an-eye-ON-ick)
• Cationic (kat-eye-ON-ick)
• Nonionic (non-eye-ON-ick)
• Amphoteric (am-fo-TERR-ick)

Alternate shampoos, sometimes labeled SLS-free, have much less harsh chemicals and none from the sulfate family. While gentler on human hair, these shampoos often have to be applied multiple times in order to effectively remove buildup.

Many shampoos are pearlescent. This effect is achieved by addition of tiny flakes of suitable materials, eg. glycol distearate (a wax).

Shampoo - Dimethicone

Dimethicone (and honey, to a lesser extent) coats the hair, filling up tiny holes and giving the hair a smoother feel and a shinier texture. It seals out moisture, thus preventing frizz and keeping flat-ironed hair straight and curled hair curly. It also protects against mechanical damage from dirt throughout the day. Because it locks out damage-repairing conditioner as well, it's better to avoid shampoos that contain lots of dimethicone if you are going to use a hair conditioner. Rather, you should apply dimethicone after conditioning with products like Frizz-Ease Hair Serum. If you choose to use them at all - by sealing out moisture, the hair becomes more prone to breakage, especially in those with dry or fine hair. Dimethicone (and other silicone derivatives) can also mask breakage by sealing the broken hair together temporarily. Many people who use a lot of dimethicone and then go without suddenly notice a lot of split ends and incorrectly attribute it to not including -cones, when the -cones were actually causing the problem in the first place.

Shampoo - Additives Useless and Otherwise

The FDA only mandates that shampoos accurately list ingredients, but doesn't mandate that any other statements be proven or even truthful. Therefore, shampoos are free to make all sorts of claims about useless ingredients, such as botanical extracts and purified waters.

Vitamins and pro-vitamins, advertised mostly by Pantene Pro-V, are only helpful if ingested. Since your hair isn't living, it can't make use of vitamins or minerals. Applying them directly to your hair will not cause damage, but may be dulling.

Amino acids are useless for your hair for the same reasons as vitamins. Some enzymes, however, can help repair your hair if used in conditioners.

Shampoo - Specialized shampoos

There are shampoos available specifically for those who have dandruff. Such shampoos contain zinc pyrithione, selenium sulfide etc. These chemicals are fungicides, and reduce dandruff by killing Malassezia furfur. Coal tar and salicylate derivatives are often used as well.

Some companies use "all-natural" or "organic" or "botanical" ingredients, such as flowers and the like, often combining these additions with a harsher base. The actual effectiveness of these organic ingredients are controversial.

Shampoo for infants is formulated so that it is less irritating to the eyes. Most contain sodium laureth sulfate, the mildest of the sulfate family. Alternatively, many infant shampoos are also formulated using other classes of surfactants, most notably non-ionics which are much milder than any charged anionics used.

Shampoo for animals (such as for dogs or cats) is often formulated so as not to irritate the animal's eyes. For this reason, baby shampoo is often an excellent substitute. Shampoo intended for animals might contain insecticides or other medications for treatment of skin conditions or parasites such as fleas or mange. It is important to note that while most human shampoos are appropriate for animal use, products that contain active ingredients/drugs such as zinc in antidandruff, are potentially toxic when ingested in large quantities by animals (but not humans) and special care should be taken to avoid use of those products on animals.

Shampoo is also available in solid form, allowing it to be rubbed onto the hair. This has the advantage of having the shampoo easily carried, but also has the disadvantage of working less efficiently on longer hair.

See also

• List of shampoo brands
• Hair conditioner

Adapted from the Wikipedia article "Shampoo", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki