For white items that have yellow stains, just mix hydrogen peroxide, baking soda, and some dawn dish soap. Once you have a paste-like mixture, use a small scrubbing brush, and apply the mixture to the area that needs treatment. Scrub it in well, and let it sit for about 30 minutes. Then throw your white items in with your other whites that need to be cleaned, and follow your normal washing and drying routine. The stains will disappear and your clothes will look really white! This works especially well for armpit stains in clothing.