How Do Shampoos Work Chemically?

Shampoo keeps your hair looking clean and healthy.

Shampoo's job is to rid hair of the various organic and inorganic materials that make it unclean. When hair is dirty, it contains skin flakes, dust, dirt, oil, salt and hair-product residue. Water alone will not fully remove these materials; shampoo is needed to restore hair back to its original health and cleanliness.

Basic Composition

Shampoo combines a surfactant, most often sodium lauryl sulfate and/or sodium laureth sulfate, with a co-surfactant to produce a viscous liquid. These help the hair become fully wet and keep oil and other impurities suspended above its surface so that they are not redistributed. Additionally, shampoo contains a soap-free detergent that reduces the surface tension of water. This allows the shampoo to penetrate tiny crevices in the scalp and hair shaft, washing away oil and buildup present in unclean hair.

Other Ingredients

In addition to detergent, shampoo contains a variety of other ingredients. Some, like salt, citric acids, fruit extracts and egg white proteins are fairly recognizable. These help thicken the hair, maintain its pH, moisturize and hydrate hair shafts and add volume, respectively.

Specialty Shampoos

Some specialty shampoos contain beer, which adds body and luster, and olive oil, which makes hair soft and shiny. Dandruff shampoos contain fungicides such as zinc pyrithione and selenium sulfide, which reduce loose dander in the hair. Baby shampoos are specially formulated to be gentler on the scalp, and will not produce a burning sensation if they come in contact with the eyes. This is usually accomplished by using less-irritating surfactants.

Perfumes

Some shampoos contain perfume. Popular scents include lavender, coconut, vanilla, peppermint, orange and freesia. While perfumes give shampoo a pleasant fragrance, they do not contain any cleansing properties.

Formulations

Modern shampoos are specially formulated for different hair types. At any pharmacy, grocery store or hair salon, shoppers will find shampoos designed for oily, wavy, dry, flat, straight and color-treated hair. It's best to choose a shampoo that is formulated for your exact hair type, ensuring that the right amount of oil is removed from your hair without compromising its softness or shine. Shampoo for color-treated hair contains a gentler detergent than other shampoos, allowing color to last longer.

References

• FDA Consumer: What Does Shampoo Do?
• Hairfinder: Exactly How Does Shampoo Clean the Hair?