The disclosure relates to a composition comprising at least one fluorescent dye and at least one non-associative thickening polymer, to processes using such a composition, and to devices comprising such a composition.The disclosure also relates to processes and methods for dyeing human keratin materials, for example artificially dyed or pigmented hair and dark skin, with a lightening effect, using compositions comprising at least one fluorescent dye and at least one non-associative thickening polymer.