Hydrolysed styrene/maleic anhydride copolymers, i.e. styrene/maleic acid, and salts thereof (e.g. cosmetically and pharmaceutically acceptable salts, such as alkali metal salts, for example potassium or sodium), of use in the present invention will typically have a monomer ratio of styrene to maleic acid of greater than 1:1, in particular greater than 1.2:1, especially greater than 1.5:1, suitably