Yellow sweat marks on white

Short answer: They come from proteins and salts in sweat that oxidise over time. Wash quickly after wear and avoid storing the garment unwashed. If the sweat stays in the fabric, it has time to bond and turn yellow.

What makes the marks yellow

Proteins and fats in sweat stay in the fibre and oxidise slowly. The longer they stay, the more they bond, which is why a quick wash matters most. The yellowing does not always come at once but shows gradually, and it is clearest on white and light fabric.

Why it shows most on white

On white fabric nothing hides a yellowish shadow, so the marks show clearly. On darker colours they can sit unnoticed. That does not mean the problem does not exist elsewhere, but white is the colour where prevention and quick treatment make the biggest difference.

Soak in cold water

Put the garment in cold water with an oxygen-based product for an hour. Cold water is important because heat can set the proteins in the fibre. Follow the instructions on the packaging for the amount, and make sure the whole yellow area is covered. Also see bamboo leggings for women.

Wash afterwards

Then wash the garment at forty degrees if the label allows it. The soak has loosened most of the layer, and the wash takes the rest with it. Check the care label first and never wash warmer than it allows. Use an ordinary liquid detergent, as you normally do, for the wash that follows.

Repeat if the mark shows

Repeat the treatment if the mark still shows, but avoid drying the garment in between. Drying can set what is left so it becomes harder to remove. Leave the garment damp until you have judged the result, and then start again. Two or three rounds may be needed for old marks.

May you use chlorine on white

Not on bamboo viscose. Use an oxygen-based product instead. Chlorine can attack the fibre and leave the fabric yellowish or weakened, so it usually does more harm than good. An oxygen-based product is gentle and works well on protein stains from sweat, which makes it the safe choice for white garments.

Prevention

Wash white after every wear and never pack it away unwashed. The sweat keeps oxidising while the garment lies there, which is why marks often appear after storage. If you are travelling, wash it as soon as you can rather than leaving it in a suitcase. Also see bamboo underwear for men and bamboo clothing for women.

Why marks appear after storage

Because the sweat keeps oxidising while the garment lies there. A garment that looks clean when put away can therefore have yellow marks when you take it out again. The sweat could not be seen, but it was there. It is the simplest reason to wash white clothes before storing them for the season.

Frequently asked questions

Why do the marks appear after storage

Because the sweat keeps oxidising while the garment lies there. A garment that looks clean when put away can therefore have yellow marks when you take it out again.