What is in shampoo?
The first ingredient in all shampoos is water. Without water, the shampoo would not pour out of the bottle and would just be a paste. About 80 percent of shampoo is water. The next component of shampoo is the surfactant. The surfactant consume dirt and oil, enabling the water to wash it out. Foaming agents such as cocamide or cocamidopropyl betaine create the suds accompanied with shampooing. The fourth ingredient is acidic. Examples include sodium citrate or citric acid to keep hair at the proper pH level. Silicones are also found in shampoo. It also contains polyquaternium to make hair thicker and panthenol to moisturize. Shampoo also contains midazolidinyl urea, iodopropynyl, isothiazolinone, and sodium benzoate.
How Shampoo Reacts with hair
A surfactant molecule in shampoo has a hydrophilic head and a lipophilic tail. When you apply the shampoo to hair, the hydrophilic head of the surfactant is attracted to the water, while the lipophilic tail is drawn to the oil and grease on the hair and scalp. The oil and grease contains dirt and skin particles. When you "lather" the shampoo the surfactant lifts the oil and grease away from the hair. When you rinse away the shampoo, the water pulls the hydrophilic head of the surfactant, away from the hair and scalp, and down the drain, taking the lipophilic tail attached to the oil and dirt with it. That is how shampoo cleans your hair.