Hi Nicola
One of the things you can do to try and alleviate the problem is to add a clarifying shampoo to your cleansing system. You could be using too many styling products and this could be causing a build-up. It often takes a while for the build-up signs to show, so check what you’re using as styling aids as well. Another less costly way to try and remove build-up and to make your clean hair last a little longer will be to add 2 tablespoons of vinegar to a litre of warm water and use it as your final rinse after washing your hair.