Underarm odour is embarrassing, and there are thousands of products that try to stop the odour before it starts. The problem is the odour is caused by bacteria in the armpits and once that bacteria is on the clothing it's very difficult to get the smell out even after washing the garment multiple times! The secret is to kill the bacteria in the cloth fibres to get rid of the bad smell. Instead of spending lots of money on store products, there are plenty of household items that can tackle the task of killing the bacteria.
Soak the garment in 4 cups of white vinegar overnight.
Machine wash the garment with laundry detergent, 2 cups of vinegar and 1/2 cup of baking soda. Dry normally.
When finished, not only the smell but any discolouration should be gone.
If there are multiple garments, instead of soaking each one, pour 4 cups of white vinegar into a spray bottle and spray the affected area until soaked through and leave overnight. Wash as shown in step 2.
Wash the clothes and dry them normally. Pour 4 cups of rubbing alcohol into a spray bottle.
Once the clothes are dry, spray the underarm area with the alcohol. Spray the area until it is well soaked.
Wait for the alcohol to dry completely. Once it is dried, the smell should have disappeared. The alcohol will kill the bacteria, which will kill the smell. Unfortunately, it will not remove stains.
Take 6 cups of undiluted 3% antibacterial hydrogen peroxide, and pour into a small bucket.
Soak the garment overnight. Wash in the washing machine as usual.
Make sure the smell is gone before drying the garment. If the odour is still there, soak it an additional 3 hours, wash again, and dry it normally. The antibacterial hydrogen peroxide will kill any bacteria causing an odour. Again, however, it will not wash out stains.
Simply add 1/2 cup of dishwasher detergent to the washing machine with the regular amount of laundry detergent.
Wash on the "hot" setting, unless the garment's tag warns against hot water use. When finished if the smell is not gone, make a paste with the dishwasher deterent by adding a little water to it. Rub it on the underarm area and let it sit for a few hours.
Put the garment back in the washing machine and wash as shown in "step 1". Once the garment is done, both smell and any stains should be removed. Dry normally.
Underarm odour and stains is made by the bacteria in the armpits. Though these are good ways to get the smell out of clothes, there are a few ways to prevent the underarms from smelling in the first place. Try putting rubbing alcohol on a cotton swab and dabbing under the arms. Or mix 1 part vinegar with 2 parts water in a spray bottle; spray under the arms and let it dry. Both ways will kill the bacteria and are long lasting.