Why is Detergent Blue?
Optical Brightener is a blue or fluorescent dye detergent manufacturers add to make clothes appear brighter and cleaner.
Do they make the clothes cleaner?
NO! Optical brighteners simply dye the yellowing on clothing to give the "appearance" of being "cleaner" they do not clean the clothes at all. In fact they only make you "feel" like the clothes are cleaner or that stains have been removed by tricking your eye. When really the yellowing fabric has only been covered up with dye.
So, what exactly are optical brighteners?
Optical Brighteners are chemical compounds that absorb light in some spectra and emit light in the blue spectrum.
But if my clothes look clean, why should I care?
Over time optical brighteners fade bright colours, makes pastels and other light colours look a bit strange, and makes white appear grey.
Since they are deposited on the clothes they can also cause skin irritation in some people besides a whole host of negative environmental effects. Optical brighteners are bio-accumulative, meaning that they can build up in the tissues of fish and other wildlife over time. This can lead to higher concentrations of these chemicals in the food chain, posing risks to predators or humans.