You’re not imagining things: Your hair can get conditioned (pardon the pun) to the shampoo you’re using, which makes it less effective. The conditioning ingredients in shampoo are attracted to the damaged spots in your hair, which is good for a while—until they build up so much they weigh your hair down. Try a deep-cleaning shampoo by a different manufacturer for a week or two, and then you can go back to your favorite brand and get the results you loved in the first place.

READ MORE: The Science of Build-Up in Hair Care Products