Shampoo

Shampoo is defined as a type of hair-care product used to remove oil, skin particles, dandruff, and other environmental pollutants that gradually build up in hair.

The word 'shampoo' means head massage in several North Indian languages. And the word was introduced to Britain from colonial India.

The word 'shampoo' in English is derived from Hindi chāmpo.

During early stages of shampoo, it is made by boiling shaved soap in water, and herbs were added to give the hair shine and flagrance.
Originally, shampoo and soap have similar properties, this is because both contains surfactants (a type of detergent).

Modern shampoo was first introduced around 1930s with Drene, the first non-soap shampoo.

So how does shampoo works?

Shampoo will strip the sebum from the hair.
Sebum is the oil secreted by hair follicles, and it will be absorbed by the hair, forming a protective layer on the hair. This will protect the hair protein from damage.

However, this protective layer tends to collect dirt and scalp flakes. Therefore surfactants in shampoo will strip the sebum from the hair, thus removing the dirt attached to the sebum layer as well.

Although both soap and shampoo contains surfactants, but soap bonds to the oils with much higher affinity, that it will remove too much oil on hair.
Shampoo contains different class of surfactants that are balanced to avoid excessive oil removal from the hair.

Shampoo formulations will normally try to maximize the following qualities:
- easy rinsing
- minimal skin or eye irritation
- no damage to hair
- pleasant flagrance
- low toxicity
- slightly acidic(pH less than 7), this is because basic environment will break the disulfide bonds in hair keratin, causing the hair to be weaken
- and more.........

Some of the common ingredients found in shampoo are:
- ammonium chloride
- ammonium lauryl sulfate
- glycol
- sodium lauryl sulfate

There are also some 'specialized' shampoo which has some other functions besides removing sebum from hair.

For example, anti-dandruff shampoo.
This type of shampoo contains fungicides( chemical compounds used to kill or inhibit fungi or fungal spores).
Fungicides that present in anti-dandruff shampoo are ketaconazole, zinc pyrithione and so on.
Those fungicides will kill the Malassezia furfur which is the main cause of dandruff.