Optical Brighteners (Fluorescent Whitening Agents)
Optical brighteners are fluorescent substances added to detergents that cling to fabric and re-emit invisible ultraviolet light as blue-white light. They do not actually clean laundry; they only make it look whiter and brighter. From a human health perspective they have low toxicity; the debate is more about their slow breakdown in the environment and their unnecessary use.
Risk range
1 is the lowest and 10 the highest risk. The range depends on the amount used, whether the product is rinsed off and how it is used. The Temiz İçerik app uses the same ranges.
It sits in the low-to-moderate range because it stays on fabric but has low toxicity; its persistence on fabric for sensitive skin and baby clothes sets the upper end, and its slow breakdown in the environment determines the overall level of the range.
What are optical brighteners and what do they do?
White fabrics gradually take on a slightly yellowish tone with time and washing. Optical brighteners do not remove this yellowing; they balance it visually: they absorb the invisible UV rays in daylight and give them back as visible light with a blue tone. Because blue and yellow cancel each other out, the fabric looks whiter and brighter to the eye.
The most commonly used ones in detergents are stilbene and biphenyl derivatives. Their effect depends on them staying attached to the fabric; in other words, their purpose is precisely to remain on the laundry after washing. The way white T-shirts glow under nightclub lights is also thanks to these substances.
Which products contain them?
- Powder and liquid laundry detergents (especially for whites and "ultra white" products)
- Some stain removers
- Paper, napkin and textile manufacturing (applied at the factory)
- Some plastics and paints
Under EU detergent legislation, detergent labels list "optical brighteners" without stating the amount. They are usually absent from detergents made for colours and wool, because they can change the shade of coloured fabric.
Are they harmful? The scientific assessment
The optical brighteners used in detergents have low acute toxicity and are not classified as carcinogens or endocrine disruptors. The amount left on fabric is very small and most of it stays firmly bound to the fabric; transfer to the skin is limited.
Although rare, skin sensitivity or irritation, particularly in combination with light, has been reported in some people. People with eczema or very sensitive skin may be more sensitive to any chemical left on fabric.
Environmentally, optical brighteners biodegrade slowly in water. On the other hand, in treatment plants they are largely removed from the water by binding to sludge, and they can break down in sunlight. Their aquatic toxicity is considered low; even so, because they are added "just for looks", their unnecessary use is being questioned.
Who should be careful?
- Baby clothes and sensitive skin: Brightener-free detergents can be chosen; since they make no functional contribution to cleaning, nothing is lost.
- Coloured and dark laundry: Brighteners can give colours a faded or greyish look.
- Silk and wool: They can cause yellowing or a change of shade in these fabrics.
What to do when you see them on a label
Using a detergent containing optical brighteners is not a problem for most people. Real whiteness requires removing dirt and stains; that job is done by enzymes and oxygen bleaches such as sodium percarbonate. If you want fewer additives, you can try a percarbonate-based, brightener-free detergent for whites and dry your laundry in the sun to benefit from its natural bleaching effect.
Frequently asked questions
Do optical brighteners clean laundry?
No. They only reflect light so that the fabric looks whiter. The substances that remove dirt and stains are surfactants, enzymes and bleaches.
Are optical brighteners harmful for baby clothes?
They have low toxicity; however, as they provide no functional benefit, a brightener-free detergent can be chosen for babies and sensitive skin.
Why are optical brighteners unwanted for coloured laundry?
The blue-white fluorescent effect can make colours look faded or greyish. That is why they are usually absent from detergents for colours.
Sources
Updated: 2026-10-11 · How we score
This page is for general information and is not personal medical advice. Warnings on the product label and the advice of a health professional always come first.