Does your armpit perspiration leave your white shirts with yellow stains? TRY SALT!
via Real Simple
“Restore yellowed cottons or linens to their original white by boiling the items for one hour in a salt-and-baking soda solution. Perspiration stains may be removed by adding 4 Tablespoons of salt [and baking soda] to 4 cups (1 liter) of hot water. If you can’t soak the item, sponge the fabric with the solution until the stains disappear.” (Green Cleaning)