Sponge on white vinegar (or soak stain in it); wait 30 minutes. Launder shirts in the hottest water safe for the fabric. Using an enzyme detergent or a detergent with bleach alternative check care labels to be sure this is okay). I sometimes put liquid laundry detergent right on the area, leave it for five to ten minutes, then wash. To prevent: Let deodorant dry before dressing. And don't let stains sit! Apply prewash spray or liquid detergent ASAP, then launder. Every third or fourth washing, use the hottest water safe for the shirts.