The Best Underarm Stain Remover Specifically formulated to remove those yellow stains and hard patches, restoring your clothing to its original appearance!
I had the same problem with all my work shirts. Normally caused by the deodorant I soaked them overnight in Vanish Oxi-action and that worked. I'm surprised it didn't work for you.
Once I had them white again I switched to Pitrock crystal deoderant, which doesn't cause the stains. It does allow you to sweat through, but stops the bacteria from forming that cause the smell. And lasts forever.