Shampoo is a staple in our bathroom for cleaning and potentially treating the scalp and hair. We tend to worry more about the type of shampoo to use than the amount to apply. However, this is a common mistake related to its use. Indeed, applying an excessive or insufficient amount of shampoo may, over time, harm the health of your hair and scalp. Here is the sufficient amount of product to use to preserve the beauty and health of your hair.