Clarifying shampoo is, for all intents and purposes, like your regular shampoo but a more deep-cleansing shampoo. Tracy Strycker from Salon Allegra informs us that all shampoos will cleanse your hair of the usual oil and residue, but a targeted clarifying formula will cut through more stubborn dirt and build up. Some of the reasons to add it to your routine is to prepare it for hair colouring, as a pre mask step, to keep blonde from turning brassie and to get rid of build up styling products etc.