There are several methods that can be used to remove yellow stains from laundry, such as applying detergent to the stain and letting it sit or using an oxygen-based stain remover. Several natural stain removal methods work on yellow stains, as well. For example, vinegar or baking soda both work well as stain removers.
Typically, yellow stains are caused by sweat and can be difficult to remove. However, pre-treating the clothing can help loosen or fade the stains. One method of pre-treatment is simply pouring undiluted vinegar or hydrogen peroxide on the stain and letting it sit for about 30 minutes. Throw the clothing in the wash as normal after pre-treating. Do not use hydrogen peroxide on colored clothing.
Another method of removing yellow stains from clothing is by rubbing a solution of baking soda, hydrogen peroxide and water on the stain. Mix equal parts baking soda, hydrogen peroxide and water together to create a paste. Rub the paste on the stain and let it sit for at least 30 minutes. Use a toothbrush to scrub and loosen the stain. Wash the clothing normally in warm or cold water. If the clothing is colorfast, adding chlorine bleach to the wash cycle may help remove any remaining stains.