Turn the shirt inside out
Rinse the underarm area with cold water
Make a paste with baking soda and water
Apply the paste to the pit stains
Let it sit for 30 to 60 minutes
Gently rub the stained area
Mix equal parts white vinegar and water
Soak the stain for 15 to 30 minutes
Wash the shirt with enzyme detergent
Use the warmest water safe for the fabric
Check the stain before drying
Repeat the treatment if needed
Avoid putting the shirt in the dryer until the stain is gone
For stubborn stains, use hydrogen peroxide and baking soda
Test any stain remover on a hidden area first