Some stains can be really tough to remove. Bleaching agents add power to the cleansing action of detergents by helping to break up and decolourise stains. Some stains that are left behind or only partially removed by surfactants can be removed by bleach.
Similar to enzymes, bleaching agents react with large stains to break them down into smaller ones that are more water-soluble. These smaller stains are more easily removed by surfactants or through the mechanical action of the washing machine.
Bleaching agents can remove the colour of stains, and help to brighten fabrics and surfaces. They achieve this by reacting with colour molecules. Colour molecules are then bound to the bleach molecules, and so the colour of the stain is removed.