Blue LED light outperforms bleach at removing yellow stains, Japanese study finds

Japanese researchers report that high‑intensity blue LED light can remove yellow stains from fabrics more effectively than household bleach or ultraviolet light, offering a potentially less chemically intensive route to restoring discoloured garments.

In laboratory tests, the team applied stains that mimic sweat, along with orange and tomato juice, to multiple fabric types, including silk. They found that exposure to visible blue light produced substantially greater stain removal than treatments with 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," said Tomohiro Sugahara, an author of the study. He said the approach avoids use of the hard chemical oxidants typically required in conventional bleaching methods, making it inherently more sustainable.

The researchers compared several cleaning strategies under controlled conditions and report that the photobleaching effect from blue LED exposure outperformed both chemical bleaching and ultraviolet treatments on the stain types and fabrics they examined. The study notes that ambient oxygen serves as the oxidant when light triggers photochemical reactions that break down stain molecules, a mechanism distinct from the direct chemical oxidation produced by common bleaching agents.

Bleach and other oxidants are widely used to remove protein‑ and pigment‑based stains but can damage fibres, fade dyes and pose environmental and handling concerns. The authors framed their blue‑light method as an alternative that could reduce reliance on those chemicals, though they did not provide a commercial device for household use in the published work.

The tests included delicate materials such as silk, suggesting the approach may be gentler on certain fabrics than conventional bleaching. The team reported consistent improvements across the stain types they evaluated, but the study did not address long‑term effects on textile strength, colourfastness in dyed garments, or safety and practicality for consumer washing machines.

The researchers recommended further work to assess scalability, safety and effectiveness across a broader range of stains, fabric blends and real‑world laundering conditions. If validated outside the laboratory, the technique could inform both domestic laundry practices and industrial textile processing that seek to reduce chemical use.

The study adds to a growing body of research exploring how targeted light sources can induce chemical changes in materials without introducing strong oxidants. Researchers cautioned that, until consumer products are developed and tested, conventional stain‑removal guidance remains the practical option for most households.