When shampoo is applied to remove sebum and dirt from your hair and scalp, it also leads to slight swelling of the hair cuticle layer. The cuticles, which normally cover the hair shafts in a tight, even formation, slightly lift away from the hair shaft. In this state, hair is more vulnerable to damage and heat. This is where conditioners show their benefits. They reduce the cuticle swelling, which once again form a tight layer with no gaps or raised cuticles. The hair is now ready for styling and will make it through the day without any serious damage. Properly conditioned hair is supple and holds on to its moisture for a dazzling shimmer.