Cara Bondi, Research Chemist at Seventh Generation, explains what optical brighteners are and why Seventh Generation doesn't use them.
A real clean shouldn't be an optical illusion. Optical brighteners are synthetic chemicals that make fabrics appear to glow in the presence of ultraviolet light. They don't have anything to do with getting things clean—they're only added to detergents to make us think our laundry is brighter and whiter than it really is. Designed to intentionally remain behind on our clothes and linens, optical brighteners rub off on our skin where they can cause a reaction that looks like sunburn. They're no fun for the environment either. Optical brighteners washed down our drains frequently survive wastewater treatment and escape into our lakes, rivers, and streams. Once there, they don't completely biodegrade and instead accumulate in fish.