Optical brighteners are ingredients which help to make fabrics look ‘whiter and brighter’. The majority of laundry detergents contain optical brighteners. Note: Optical Brighteners (OBAs) are also called fluorescers or fluorescent whitening agents (FWAs). If you would like you use a laundry detergent product without optical brighteners use Omo Colour. It has been especially formulated to ensure your coloured clothes stay vibrant.