Shampoo
The ingredients in shampoo are carefully chosen and combined to result in clean, manageable hair.
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Many people begin their morning routines with a shower before starting in on the day’s activities. The shampoo that they grab contains a carefully formulated combination of chemicals designed to remove accumulated dirt, oil, dandruff, and other environmental contaminants that build up in hair. Shampoos should clean effectively, cause minimal eye and skin irritation, smell pleasant, and ideally, be nontoxic and biodegradable in the environment.
Like laundry detergent and dish detergent, the fundamental component of shampoo is a surfactant, which acts as the cleaning workhorse. Surfactants assist in completely wetting the hair, creating lather, and dissolving oil and dirt to make them soluble in water so they can be washed away. However, unlike the surfactants in laundry detergents, optimized for basic pH, shampoos generally contain higher levels of acidity due to the disulfide bonds in the hair’s keratin, which are broken under basic conditions. Shampoos generally feature anionic surfactants, such as sodium lauryl sulfate or sodium laureth sulfate. In contrast, conditioners applied after shampooing contain cationic surfactants, which have the opposite charge from both the shampoo and from the keratin of the hair. The cationic surfactant does not completely wash out and coats the cuticle of the hair, making it smoother and easier to comb.
Shampoos can also contain ingredients formulated for specialized uses. Shampoos for oily hair contain more surfactant than those for dry or damaged hair. Baby shampoos contain a gentler surfactant in smaller amounts and have a pH closer to the neutral pH of natural tears to avoid eye irritation. Dandruff shampoos contain a fungicide as well to reduce dander. Although shampoo seems like a very ordinary household product, a considerable amount of chemistry comes together to clean hair.
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