The shampoo is a hair care product, typically in the form of a viscous liquid used for cleaning hair. Less commonly, shampoo is available in bar form, like a bar of soap. The shampoo is used by applying it to wet hair, massaging the product into the scalp, and then rinsing it out. Some users may follow a shampooing with the use of a hair conditioner.

The typical reason for using shampoo is to remove the unwanted build-up of sebum in the hair without stripping out so much as to make hair unmanageable. The shampoo is generally made by combining a surfactant, most often Sodium Lauryl Sulfate or Sodium Laureth Sulfate, with a co-surfactant, most often Cocamidopropyl betaine in water. The sulfate ingredient acts as a surfactant, essentially heavy-duty soap that makes it easier to trap oil and grease.

Specialty shampoos are marketed to people with dandruff, color-treated hair, gluten or wheat allergies, an interest in using an organic product, infants, and young children ("baby shampoo" is less irritating). There are also shampoos intended for animals that may contain insecticides or other medications to treat skin conditions or parasite infestations such as fleas.

Etymology
The word shampoo entered the English language from the Indian subcontinent during the colonial era. It dated 1972 and was derived from Hindi chāmpo, derived from the Sanskrit root chapati, which meant to press, knead, or soothe.

History
Indian subcontinent
In the Indian subcontinent, a variety of herbs and their extracts have been used as shampoos since ancient times. A very effective early shampoo was made by boiling Sapindus with dried Indian Gooseberry (amla) and a selection of other herbs, using the strained extract. Sapindus, also known as soapberries, is a tropical tree widespread in India, is called ksuna in ancient Indian texts, and its fruit pulp contains saponins which are a natural surfactant. The extract of soapberries creates a lather which Indian texts called phenaka. It leaves the hair soft, shiny, and manageable. Other products used for hair cleansing were shikakai (Acacia concinna), hibiscus flowers, ritha (Sapindus mukorossi). Guru Nanak, the founder and the first Guru of Sikhism, referred to the soapberry tree and soap in the 16th century.

Cleansing the hair and body massage (champu) during one's daily bath was an indulgence of early colonial traders in India. When they returned to Europe, they introduced the newly learned habits, including the shampoo's hair treatment.

Europe
Sake Dean Mahomed, an Indian traveler, surgeon, and entrepreneur, is credited with introducing the practice of shampoo or "shampooing" to Britain. In 1814, Mahomed, with his Irish wife Jane Daly, opened the first commercial "shampooing" vapour masseur bath in England, in Brighton. He described the treatment in a local paper as "The Indian Medicated Vapour Bath (type of Turkish Bath), a cure to many diseases and giving full relief when everything fails; particularly Rheumatic and paralytic, gout, stiff joints, old sprains, lame legs, aches and pains in the joints".

During the early stages of shampoo in Europe, English hair stylists boiled shaved soap in water and added herbs to give the hair shine and fragrance. Commercially made shampoo was available from the turn of the 20th century. A 1914 advertisement for Canthrox Shampoo in American Magazine showed young women at camp washing their hair with Canthrox in a lake; magazine advertisements in 1914 by Rexall featured Harmony Hair Beautifier and Shampoo.

In 1900 German perfumer and hairstylist Josef Wilhelm Rausch, develops in Emmishofen, Switzerland the first liquid hair washing soap and names it "Champooing". Later in 1919 J.W.Rausch develops an antiseptic Chamomile Shampooing (pH 8.5).

In 1927, liquid shampoo were very similar products; both containing the same naturally derived surfactants, a type of detergent. The modern shampoo is first introduced in the 1930s with Drene, the first shampoo using synthetic surfactants instead of soap. The shampoo is also more beneficial for the hair roots.

Indonesia
Early shampoos used in Indonesia were made from the husk and straw (merang) of rice. The husks and straws were burned into ash, and the ashes (which have alkaline properties) are mixed with water to form lather. The ashes and lather were scrubbed into the hair and rinsed out, leaving the hair clean, but very dry. Afterward, coconut oil was applied to the hair to moisturize it.

Philippines
Filipinos have been traditionally using gugo before commercial shampoos were sold in stores. The shampoo is obtained by soaking and rubbing the bark of the vine Gugo (Entada phaseoloides), producing a lather that cleanses the scalp effectively. Gugo is also used as an ingredient in hair tonics.

Pre-Columbian North America
Certain Native American tribes used extracts from North American plants as hair shampoo; for example, the Costanoans of present-day coastal California used extracts from the coastal woodfern, Dryopteris expansa.

Pre-Columbian South America
Before quinoa can be eaten the saponin must be washed out from the grain before cooking. Pre-Columbian Andean civilizations used this soapy by-product as shampoo.

Composition
The shampoo is generally made by combining a surfactant, most often Sodium Lauryl Sulfate or Sodium Laureth Sulfate, with a co-surfactant, most often Cocamidopropyl betaine in water to form a thick, viscous liquid. Other essential ingredients include salt (Sodium Chloride), which is used to adjust the viscosity, a preservative, and fragrance. Other ingredients are generally included in shampoo formulations to maximize the following qualities:

• Pleasing Foam
• Ease of Rinsing
• Minimal Skin and Eye Irritation
• Thick or Creamy Feeling
• Pleasant Fragrance
• Low Toxicity
• Good Biodegradability
• Slight acidity (pH less than 7)
• No Damage to Hair
• Repair of Damage already done to the hair

Many shampoos are pearlescent. This effect is achieved by the addition of tiny flakes of suitable materials, e.g., glycol distearate, chemically derived from stearic acid, which may have either animal or vegetable origins. Glycol distearate is a wax. Many shampoos also include silicone to provide conditioning benefits.

Commonly Used Ingredients

• Ammonium chloride
• Ammonium lauryl sulfate
• Glycol
• Sodium Laureth Sulfate is derived from coconut oils and is used to soften water and create a lather. There was some concern over this particular ingredient circa 1998 as evidence suggested it might be a carcinogen, and this has yet to be disproved, as many sources still describe it as irritating to the hair and scalp.
• Sodium Lauryl Sulfate
• Sodium lauroamphoacetate is naturally derived from coconut oils and is used as a cleanser and counter-irritant. This is the ingredient that makes the product tear-free.
• Polysorbate 20 (abbreviated as PEG(20)) is a mild glycol-based surfactant that is used to solubilize fragrance oils and essential oils, meaning it causes the liquid to spread across and penetrate the surface of a solid (i.e., hair).
• Polysorbate 80 (abbreviated as PEG(80)) is a glycol used to emulsify (or disperse) oils in water (so the oils do not float on top like Italian salad dressing.
• PEG-150 distearate is a simple thickener.
• Citric acid is produced biochemically and is used as an antioxidant to preserve the oils in the product. While it is a severe eye-irritant, the Sodium Lauroamphoacetate counteracts that property. Citric acid is used to adjust the pH down to approximately 5.5. It is a fairly weak acid which makes the adjustment easier. Shampoos usually are at pH 5.5 because, at slightly acidic pH, the scales on a hair follicle lie flat, making the hair feel smooth and look shiny. It also has a small amount of preservative action. Citric acid, as opposed to any other acid, will prevent bacterial growth.
• Quaternium-15 is used as a bacterial and fungicidal preservative.
• Polyquaternium-10 has nothing to do with the chemical quaternium-15; it acts as the conditioning ingredient, providing moisture and fullness to the hair.
• Di-PPG-2 myreth-10 adipate is a water-dispersible emollient that forms clear solutions with surfactant systems.
• Chloromethylisothiazolinone or CMIT is a powerful biocide and preservative.

Health Risks
Several contact allergens are used as ingredients in shampoos, and contact allergy caused by shampoos is well known. Patch testing can identify ingredients to which patients are allergic, after which a physician can help the patient find a shampoo that is free of the ingredient to which they are allergic. The US bans 11 ingredients from shampoos, Canada bans 587, and the EU bans 1328.

Specialized Shampoos
Dandruff
Cosmetic companies have developed shampoos specifically for those who have dandruff. These contain fungicides such as ketoconazole, zinc pyrithione, and selenium disulfide, which reduce loose dander by killing fungi like Malassezia furfur. Coal tar and salicylate derivatives are often used as well. Alternatives to medicated shampoos are available for people who wish to avoid synthetic fungicides. Such shampoos often use tea tree oil, essential oils, or herbal extracts.

Colored Hair
Many companies have also developed color-protection shampoos suitable for colored hair; some of these shampoos contain gentle cleaners according to their manufacturers.

Baby
Shampoo for infants and young children is formulated so that it is less irritating and usually less prone to produce a stinging or burning sensation if it were to get into the eyes. For example, Johnson's Baby Shampoo advertises under the premise of "No More Tears". This is accomplished by one or more of the following formulation strategies.

1. Dilution, in case the product comes in contact with eyes after running off the top of the head with minimal further dilution.
2. Adjusting pH to that of non-stress tears, approximately 7, which may be a higher pH than that of shampoos which are pH adjusted for skin or hair effects, and lower than that of shampoo made of soap.
3. The use of surfactants, alone or in combination, are less irritating than those used in other shampoos (e.g., Sodium lauroamphoacetate).
4. Use of nonionic surfactants of the form of polyethoxylated synthetic glycolipids and polyethoxylated synthetic monoglycerides, which counteract the eye sting of other surfactants without producing the anesthetizing effect of alkyl polyethoxylated or alkylphenol polyethoxylated.

The distinction in 4 above does not completely surmount the controversy over the use of shampoo ingredients to mitigate eye sting produced by other ingredients, or the use of products so formulated. The considerations in 3 and 4 frequently result in a much greater multiplicity of surfactants being used in individual baby shampoos than in other shampoos, and the detergency or foaming of such products may be compromised thereby. The monoionic sulfonated surfactants and viscosity-increasing or foam stabilizing alkanolamides seen so frequently in other shampoos are much less common in the better baby shampoos.

Sulfate-free Shampoos
Sulfate-free shampoos are composed of natural ingredients and free from both Sodium Lauryl Sulfate and Sodium Laureth Sulfate. The purpose of these sulfates is to create a lathering effect to remove oil and dirt from your hair. If your shampoo easily makes a lather in the shower, there is a good chance it contains sulfates. Sulfate-free shampoos make little to no lather.

Types of Shampoos
Solid
Solid shampoos or shampoo bars use as their surfactants soaps or other surfactants as solids. They have the advantage of being spill-proof. They are easy to apply; one may simply rub the bar over wet hair, and work the soaped hair into a low lather.

Jelly and gel
Stiff, non-pourable clear gels to be squeezed from a tube were once popular forms of shampoo and can be produced by increasing a shampoo's viscosity. This type of shampoo cannot be spilled, but unlike a solid, it can still be lost down the drain by sliding off wet skin or hair.

Paste and cream
Shampoos in the form of pastes or creams were formerly marketed in jars or tubes. The contents were wet but not completely dissolved. They would apply faster than solids and dissolve quickly.

Antibacterial
Antibacterial shampoos are often used in veterinary medicine for various conditions, as well as in humans before some surgical procedures.

References;
1. Shampoo