Combine one part Dawn dish soap with two parts hydrogen peroxide. Add enough baking soda to make a paste. Rub it into the perspiration stain and let it sit for an hour before washing. Be sure to rinse before washing!!
Goodbye to Yellow Armpit Stains! - stain remover mixture consisting of one part Dawn dishwashing liquid mixed with two parts HYDROGEN PEROXIDE - used the above “recipe” PLUS added some baking soda (of course!) for the extra scrubbing element…and I used a small laundry brush to work the whole concoction into the stain for a few minutes. After that I walked away and let the whole thing sit there for an hour or so and then laundered as usual.
Get Rid of Underarm Stains with Dishwashing Detergent and Hydrogen Peroxide (Plus, Other DIY Cleaning Solutions)
The armpit stain removal trick requires mixing just one part dishwashing liquid (it says Dawn, but you can probably use any brand) with two parts hydrogen peroxide, then let the mixture sit on the stain for an hour. For the worst kinds of stains, add baking soda and scrub. In no time no one would guess you were exercising in those clothes!