If you ask some hair stylists what shampoos they use for themselves or for their clients, everyone will tell you the same thing: a sulfate-free shampoo. This is because sulfates (which occur mostly in some shampoos) damage your hair.
They are not only harsh on the hair, but also remove from them the dye, hydration or natural oils - very necessary for healthy and beautiful hair. Admittedly, sulfates clean hair better, but they are also the enemy of healthy, shiny and hydrated hair.
So, the next time you buy a shmapo, pay attention to the ingredients and choose one without sulfate. After a while you will notice the change in the way your hair will look.