Your hair doesnt get used to shampoo over time

If you notice your shampoo isnt working quite as well as it used to, dont toss the bottle. You hair changes with the seasons, so that might account for a difference in texture, says Ouidad. Or, if you arent rinsing thoroughly enough, there might be a buildup of product on your scalp. It has nothing to do with the shampoo not working for you anymore. You dont change your face cleanser, so why would you change your shampoo?