Yellow sweat stains are a white shirt’s worst enemy.
And it’s tempting to reach for the bleach when you first notice them.
But now, experts have revealed another strategy to get rid of the stubborn marks and restore clothes to their former glory.
And all it requires is a blue LED light.
Japanese researchers tested different methods of removing stains caused by orange juice, tomato juice and sweat-like substances on multiple fabrics, including silk.
They discovered the most effective was high-intensity blue LED light – which removed stains substantially more than bleach or UV exposure.
‘Our method utilises visible blue light in combination with ambient oxygen, which acts as the oxidising agent to drive the photobleaching process,’ author Tomohiro Sugahara said.
‘This approach avoids the use of hard chemical oxidants typically required in conventional bleaching methods, making it inherently more sustainable.’
There’s nothing worse than having your favourite white shirt ruined by sweat stains – but scientists say the best way to deal with them doesn’t involve bleach (stock image)
Exposing a sweat-like stain on cotton (left) to a blue LED light for 10 minutes significantly removed the yellow color (right)
Yellow stains on clothes are caused by squalene and oleic acid from skin oils and sweat.
For their experiment, the researchers applied squalene onto cotton fabric swatches and heated them to simulate the passing of time.
They then treated the samples for 10 minutes, either by soaking them in a hydrogen peroxide (bleach) solution or exposing them to UV light or blue LED light.
Analysis revealed the blue light reduced the yellow stain substantially more than the hydrogen peroxide or UV exposure.
In fact, UV exposure generated some new yellow-coloured compounds.
Additional tests showed that the blue LED treatment lightened squalene stains on silk and polyester without damaging the fabrics.
The method also reduced the colour of other stain-causing substances, including aged oleic acid, orange juice and tomato juice, on cotton swatches.
The scientists said they want to commercialise a light system for home and industrial use – but need to do additional safety testing first.
It might be tempting to reach for the bleach, but a bright blue LED light was found to be more effective on stains during experiments (stock image)
Writing in the journal ACS Sustainable Chemistry & Engineering, the team said: ‘Textile bleaching methods for commercial and domestic use, such as hydrogen peroxide bleaching, often depend on oxidizing agents, solvents, and heat, making them unsuitable for delicate fabrics and demanding large amounts of energy and chemicals.
‘This study presents a new photobleaching method for removing yellow stains from clothing.
‘This technology reduces the environmental impact of bleaching by avoiding conventional oxidizing agents such as hydrogen peroxide (bleach).
‘Its solvent-free nature enables its use on delicate textiles, making it a promising sustainable cleaning method.’
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