Armpit stains can make even the nicest designer shirt look shabby. These stains are difficult to avoid, but in many cases they can be removed. In some cases, the stains are caused by sweating. In other cases these stains are caused by a mix of sweat with chemicals in antiperspirants. In either case, throwing the shirt in the wash is rarely sufficient to wash the stains away. However, if you want to save the shirt from the garbage can, a combination of the right laundry stain products and a little extra effort is often all it takes.
Pour 1 tbsp. of white vinegar and 1 cup of warm water in a measuring cup. Place the shirt on a waterproof surface and pour the vinegar and water over the stains.
Leave the shirt with this solution on it for 30 minutes. Rinse it under cool water.
Treat the stains with a pre-wash stain treatment spray or roll-on. Put the product on both the outside and inside of the shirt. If the shirt is a colored fabric, make sure to test the stain treatment product in a hidden place first to make sure the solution won't discolor the fabric.
Wait for a few minutes and machine wash the shirt in cold water with laundry detergent.
Check the stained area after it has been laundered. If any trace of stain remains, treat it again with the stain product and re-wash with detergent. Hang it to dry.