How to Remove Perspiration Stains from Clothing. Nothing is quite as unsightly as a dingy yellow perspiration stain on your shirt. Not only are these under-arm stains ugly, but they can weaken the garment's fabric - and harbor objectionable odors! Your best bet is to treat these problem areas before the stains set in.
Pre-treat new stains with a enzyme pre-soak product before laundering as usual. Make sure fabric is not linen, silk, or wool. These fabrics can shrink, bleed colors or get water circles in this process.
Refrain from putting the garment in the dryer, if the stain didn't come out. Drying it will heat-set the stain. Sponge the area with a solution of 1 tbsp. ammonia and 1/2 cup water and allow to air dry.
Treat older stains by sponging the area with a solution of 1 tbsp. white vinegar and 1/2 cup water. Old stains may be impossible to remove.
Remove lingering perspiration odor by soaking the entire garment overnight in a gallon of warm salt water (use about 4 tablespoons of salt per gallon of water).