The word shampoo was added to the English language in the year 1762. The word implied massage, which means kneading or pressing the muscles.

Initially, shampoos were made by boiling soap in water and adding herbs to it to impart health and fragrance to hair. Shampoos were originally considered to be similar to soaps because they were made from surfactants, which is a detergent. However, shampoos soon evolved as hygiene products specifically meant for hair. Unlike soap, shampoo has a rich and delicate bubbling ability that enables easy rinsing. It is mild on skin and eyes, doesn't damage hair, is low on toxicity and it is more biodegradable.

Shampoos contain synthetic surfactants that can be made in different varieties for different hair types. The surfactants present in shampoos help clean the hair by stripping sebum. Sebum is naturally occurring oil that coats the hair, thereby making it vulnerable to collect dirt and scalp flakes. Also known as wetting agents, these surfactants or "Surface Active Agent" present in shampoos lower the surface tension in the liquid with which they are mixed, thereby making spreading easy. The surfactants are anionic, cationic, non-ionic and amphoteric.

The hair-cleansing mechanism that using a shampoo enables is complex. When applied to wet hair, the hydrophobic tails of the anionic surfactants are absorbed onto the hair shaft, while their negative heads move outwards. Non-polar materials (such as grease or oil) attached to the hair shaft get displaced. Other particulate matter is easily removed through rinsing.

There are different types of shampoos for various hair types and for diverse hair-related problems such as dandruff, dryness and hair-loss, and healthier scalp. Natural shampoos, with botanical or organic ingredients are the most preferred. Shampoos are not just for people; there are specialized shampoos available for dogs and other animals too.