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From Wikipedia, the free
encyclopedia Shampoo is a hair
care product used for the removal of oils, dirt, skin particles, dandruff,
environmental pollutants and other contaminant particles that gradually
build up in hair. The goal is to remove the unwanted build-up without
stripping out so much as to make hair unmanageable.
Shampoo, when lathered with water, is a surfactant, which, while cleaning
the hair and scalp, can remove the natural oils (sebum) which lubricate the
hair shaft.
Shampooing is frequently followed by the use of conditioners which increase
the ease of combing and styling.
The word shampoo in English is derived from
Hindi chāmpo (चाँपो [tʃãːpoː]),[1] and dates to 1762.[2] The Hindi word
referred to head massage, usually with some form of hair oil.[3] Similar
words also occur in other North Indian languages. The word and the service
of head massage were introduced to Britain by a Bengali entrepreneur Sake
Dean Mahomed. Dean Mahomed introduced the practice to Basil Cochrane's
vapour baths while working there in London in the early 1800s, and later,
together with his Irish wife, opened "Mahomed's Steam and Vapour Sea Water
Medicated Baths" in Brighton, England. His baths were like Turkish baths
where clients received an Indian treatment of champi (shampooing), meaning
therapeutic massage. He was appointed ‘Shampooing Surgeon’ to both George IV
and William IV.[4]
In the 1860s, the meaning of the word shifted from the sense of massage to
that of applying soap to the hair.[5] Earlier, ordinary soap had been used
for washing hair[6]. However, the dull film soap left on the hair made it
uncomfortable, irritating, and unhealthy looking.
During the early stages of shampoo, English hair stylists boiled shaved soap
in water and added herbs to give the hair shine and fragrance. Kasey Hebert
was the first known maker of shampoo, and the origin is currently attributed
to him. Commercially made shampoo was available from the turn of the
century. A 1914 ad for Canthrox Shampoo in American Magazine showed young
women at camp washing their hair with Canthrox in a lake; magazine ads in
1914 by Rexall featured Harmony Hair Beautifier and Shampoo[7]
Originally, soap and shampoo were very similar products; both containing
surfactants, a type of detergent. Modern shampoo as it is known today was
first introduced in the 1930s with Drene, the first shampoo with synthetic
surfactants.
How shampoo works
Shampoo cleans by stripping sebum from the hair. Sebum is an oil secreted by
hair follicles that is readily absorbed by the strands of hair, and forms a
protective layer. Sebum protects the protein structure of hair from damage,
but this protection comes at a cost. It tends to collect dirt, styling
products and scalp flakes. Surfactants strip the sebum from the hair shafts
and thereby remove the dirt attached to it.
While both soaps and shampoos contain surfactants, soap bonds to oils with
such affinity that it removes too much if used on hair. Shampoo uses a
different class of surfactants balanced to avoid removing too much oil from
the hair.
The chemical mechanisms that underlie hair cleansing are similar to those of
traditional soap. Undamaged hair has a hydrophobic surface to which skin
lipids, such as sebum, stick, but water is initially repelled. The lipids do
not come off easily when the hair is rinsed with plain water. The anionic
surfactants substantially reduce the interfacial surface tension and allow
for the removal of the sebum from the hair shaft. The non-polar oily
materials on the hair shaft are solubilised into the surfactant micelle
structures of the shampoo and are removed during rinsing. There is also
considerable removal through a surfactant and oil "roll up" effect.
[edit] Composition
Shampoo formulations seek to maximize the following qualities:
* Easy rinsing
* Good finish after washing hair
* Minimal skin/eye irritation
* No damage to hair
* Feels thick and/or creamy
* Pleasant fragrance
* Low toxicity
* Good biodegradability
* Slightly acidic (pH less than 7), since a basic environment weakens the
hair by breaking the disulfide bonds in hair keratin.
Many shampoos are pearlescent. This effect is achieved by addition of tiny
flakes of suitable materials, eg. glycol distearate, chemically derived from
stearic acid, which may have either animal or vegetable origins. Glycol
distearate is a wax.
Ingredient claims
In the USA, the Food and Drug Administration (FDA) mandates that shampoo
containers accurately list ingredients. The government further regulates
what shampoo manufacturers can and cannot claim as any associated benefit.
Shampoo producers often use these regulations to challenge marketing claims
made by competitors, helping to enforce these regulations. While the claims
may be substantiated however, the testing methods and details of such claims
are not as straightforward. For example, many products are purported to
protect hair from damage due to ultraviolet radiation. While the ingredient
responsible for this protection does block UV, it is not present in a high
enough concentration to be effective. Shampoos made for treating medical
conditions such as dandruff are regulated as OTC drugs[9] in the US
marketplace. In other parts of the world such as the EU, there is a
requirement for the anti-dandruff claim to be substantiated, but it is not
considered to be a medical problem.
Vitamins and Amino Acids
The effectiveness of vitamins, amino acids and "pro-vitamins" to shampoo is
also largely debatable. Vitamins and amino acids are the building blocks of
proteins and enzymes within the body. While vitamins may be able to
penetrate cells through the skin, amino acids and proteins are too large to
enter a cell outside the bloodstream, and they can have no effect on dead
tissue. Proteins are constructed from amino acids following an RNA blueprint
inside the cell. A strand of hair is a long protein chain continually being
added to at the root. The only way for an amino acid to be of any use is to
be intentionally bound to other amino acids in a specific fashion by a
living cell. Hair is not alive, and there is no possibility for an amino
acid or protein to have any permanent effect on the health of the
strand.[citation needed]
The case for vitamins is not as well understood. Some have demonstrated a
moderate effectiveness in improving the health of skin,[10] but most likely
the benefit is derived from the effect of vitamins on living cells below the
epidermis. Extending this benefit to hair, the vitamins and minerals could
improve the health of new hair growth, but the benefit to existing hair is
unsubstantiated. However, the physical properties of some vitamins (like
vitamin E oil or panthenol) would have a temporary cosmetic effect on the
hair shaft while not having any bioactivity. |
