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.[18][19] 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[20]
low toxicity
good biodegradability
slight acidity (pH less than 7)
no damage to hair
repair of damage already done to hair
Many shampoos are pearlescent. This effect is achieved by 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.