Eat cleansing foods, drinks lots of water, herbal teas like burdock and dandelion and use a sauna to detox. I used to have horrid underarm odor, but since I have begun detoxifying using a far infrared and castor oil to my underarms and changing my diet to mostly vegetables and a few grains, the odor is gone.
I am convinced that odor comes from the liver's inability to detox properly.