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The human body cools itself through the process of perspiration. Releasing what is commonly known as sweat through the skin glands causes evaporation at the surface of the skin, which helps the body to cool down. Sweat is 99 percent water and is, in and of itself, not scented. However, moist dark environments such as those found in the arm pits or genitals encourage the growth of bacteria. As the bacteria grow, they emit noxious chemicals which are responsible for the pungent odor associated with sweat. These chemicals are easily absorbed by fabrics, particularly those made of natural fibers such as cotton. Once absorbed, the chemicals found in sweat can lead to discoloration of the material and can leave a lingering aroma.
Soak the garment in question. Fill a bucket with warm water and add 1 cup of baking soda to the water. Stir until the baking soda is completely dissolved and then place the clothing in the bucket. Press down on the garment with your hands to ensure it is fully submerged and allow it to soak for 24 to 48 hours.
Combine ¼ cup of cool water and ¼ cup household ammonia. Stir until well combined. Use an old cloth or damp sponge to apply the ammonia solution directly onto any areas of fabric that still smell like body odor. Dampen the affected areas thoroughly and then set the treated garment aside, allowing it to dry at room temperature for one hour.
Launder the clothing according to the manufacturer's instructions. These can generally be found on the garment's tag. Stop the machine just prior to the beginning of the rinse cycle and add 2 cups of distilled white vinegar to the water. Allow the clothing to soak in the vinegar rinse for 1 hour and then re-start the machine, allowing the rinse cycle to finish.
Dry freshly laundered clothing outside on a clothes line or on a clothes rack placed in direct sunlight. Alternatively, hang clothing in front of a fan in a sunny room to help imitate the action of the open air. If you must use a dryer, use the lowest heat setting possible as heat can cause odoriferous chemicals to bond with fabric fibers.
Repeat if necessary. Wait until the clothes are completely dry and then check them for lingering body odor. One time through the treatment process should remove most odors, but chemicals which have been "set" into the fabric may take several cycles to completely remove.