Lay a paper towel down on a flat work surface. Place the ink-stained area of the shirt face down against the paper towel.
Dampen cotton balls with rubbing alcohol and sponge the backside of the ink stain, pressing the shirt against the paper towel. As the ink stain transfers to the towel change it with a clean paper towel. Continue this process until the majority of the ink stain is removed.
Discard the soiled paper towels in the trash. Turn the shirt over so the ink stain is facing up.
Spray the remaining ink stain with an aerosol pretreatment spray. Let the spray soak into the fabric for two to three minutes.
Wash the shirt with laundry detergent and all-fabric bleach to remove the last traces of the felt tip pen ink stain. If traces of the stain remain, treat it by dabbing the shirt with dry cleaning solvent. Allow the solvent to dry on the shirt and launder with detergent and all-fabric bleach. Make sure the stain is completely gone before air drying the shirt.