What are optical brighteners in clothing and are they harmful?

Optical brighteners (also called fluorescent whitening agents) are chemical compounds added to fabrics and laundry detergents to make whites appear brighter and colors more vivid. They work by absorbing ultraviolet light and re-emitting it as visible blue light, creating the illusion of brightness. They are widely used in white shirts, bedsheets, and underwear.

Optical brighteners remain on fabric as a residual coating and can transfer to skin, where they have been linked to skin irritation and photoallergic reactions, meaning skin becomes more sensitive to sunlight in the areas where the chemical is present. Some optical brighteners have shown low-level estrogenic activity in laboratory studies, raising endocrine disruption concerns.

GOTS-certified organic textiles prohibit optical brighteners, and OEKO-TEX tests for their presence. If you notice that white clothing seems unnaturally bright or glows under UV/blacklight, it likely contains optical brighteners. Choosing naturally colored or undyed fabrics, or GOTS-certified whites, avoids this unnecessary chemical exposure. ONDU's brands rely on naturally white or low-impact dyed fabrics.