Shampoo is a hair care product, typically in the form
of a viscous liquid, that is used for cleaning hair. Less commonly,
shampoo is available in solid bar format. 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 hair
conditioner. Shampoo is typically used to remove the unwanted build-up
of sebum in the hair without stripping out so much as to make hair
unmanageable. 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, trapping oils and other contaminants,
similarly to soap. Shampoos are marketed to people with hair. There
are also shampoos intended for animals that may contain insecticides
or other medications to treat skin conditions or parasite infestations
such as fleas.