Soak the garment in cool water, or wet the stained areas for at least 15 seconds.
Allow the garment to air dry completely before applying detergent.
Pour the enzyme-rich liquid laundry detergent onto the stained areas of the garment. Grab each garment on both sides of the stain, and scrub the surfaces of the armpit area against themselves to work in the detergent. Repeat the scrubbing for the other side of the garment.
Allow the detergent-permeated garment to stand for at least 15 minutes.
Add laundry detergent and chlorine bleach to your washing machine, and set it for the highest-temperature wash cycle available. Use 3/4 cup bleach in a standard-size washing machine. Use 1 1/4 cup bleach for laundry in an extra-large washing machine.
Wash all of the white garments you treated for armpit stains in a single load.