Sweat stains on your white shirts are bound to happen. When sweat stains form on white shirts, they often take on a discoloured, yellow appearance, which makes the shirts look dirty even when they're actually clean. Sweat stains contain proteins, so the best way to tackle sweat stains on your white shirts is to break down the proteins in the stains for easier removal.
Lay an old towel on your work surface. Place your sweat-stained white shirt on the towel with the sweat stains facing up. Pour undiluted hydrogen peroxide onto the sweat stains.
Allow the shirts to sit with the peroxide on them for 30 minutes. The peroxide will break down the protein in the sweat stains. Flush the fabric with cool water.
Pour oxygen liquid washing powder on the remaining sweat stains. Use enough to cover the stains. Rub the detergent into the stain and the fibres of the fabric by rubbing the fabric together.
Place your white shirts in the sun. Allow the washing powder to soak into the fibres while the sun bleaches the sweat stains. Mist the stained areas with plain water to keep the fabric moist. Allow your white shirts to sit in the sun for a few hours.
Launder your white shirts in cool water with oxygen washing powder. Add 1/2 cup baking soda to the wash water to tackle any sweat odour. Line-dry your white shirts, preferably outdoors.
Switch antiperspirants every three months, as they eventually tend to lose effectiveness.
Avoid the use of bleach on a sweat stain, as it may turn the stain more yellow.