Most think sweat stains are caused by sweat, but they are actually the result of a reaction between aluminum-based antiperspirants and your body. To attack the discoloration, soak the shirt in a bowl filled with the vinegar and two cups warm water. Soak for at least 20 minutes.
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Image Source: POPSUGAR Photography / Sarah Lipoff
Mix together the baking soda, salt, and hydrogen peroxide until it forms a paste. Remove the shirt from the vinegar water and gently squeeze until the shirt is just damp. Lay flat on a towel-covered work surface and coat the stains with the mixture. Hydrogen peroxide is a natural whitening agent, and baking soda and salt work together to lift the stain. Let sit for at least 20 minutes.
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Image Source: POPSUGAR Photography / Sarah Lipoff
Toss the shirt in the laundry with a load of whites and wash. Voilà! Now you can take off your jacket and raise your arms without worrying about flashing nasty stains.