Apply a hydrogen peroxide and baking soda paste

Mix equal parts 3% hydrogen peroxide, baking soda, and water into a thick paste, spread it over the yellow stains, and scrub gently with an old toothbrush before washing.

Why It Works

Hydrogen peroxide is a mild oxidizing bleach that breaks down the chemical bonds in sweat-and-deodorant residue (primarily aluminum salts reacting with proteins). Baking soda adds gentle abrasion to lift the stain from fabric fibers while also neutralizing odor. The combination targets both the discoloration and the buildup that causes it.

Tips

• Let the paste sit for 30-60 minutes before washing for best results
• Wash in warm water (check the care label first) to help dissolve residue
• Always check that the stain is gone before putting the shirt in the dryer, as heat sets stains permanently
• Test on an inside seam first with colored fabrics, since peroxide can lighten dyes