Most people think that a good shampoo is one that produces lots of lather and bubbles. However, when these bubbles are formed it is because of surfactant molecules forming around air rather than oil and dirt molecules.
Surfactants are the ingredient in shampoos that helps to cleanse the scalp and hair by removing dirt. There are several different types of surfactant:
Anionic surfactants are the most commonly used as they are the most thorough, but can cause irritation on the scalp. Cationic surfactants are not used as often, especially not in high concentrations as they are dangerous to the eyes, but recently it has been possible to mix cationic surfactants in low concentrations with anionic ones.