General Sweat Stains
If you've got sweat stains on colored clothes or shoes, one of your best options might be under your kitchen sink. Dawn dish soap—powerful enough to eradicate oil, but gentle enough for those baby ducks—is a highly effective stain remover. Especially for oily, grimey sweat stains. Scrub the dish soap into the stain (preferably with a small brush) and let it soak in for 10 to 30 minutes before throwing in the washer. The cleaning agents in the soap actually pull away and hold the sweaty grease until it's washed away in the rinse cycle.
If you're noticing yellowing in the pits of your white shirts, you can probably blame your deodorant or antiperspirant. (Let this be a reminder that you don't need to go overboard when applying to your underarms.) Melissa Maker, founder of Clean My Space, has tested every possible solution and says that an old fashioned home remedy works best: She suggests a paste made from one part baking soda and two parts hydrogen peroxide. Pre-treat the soiled areas and let it sit for at least 20 minutes (up to overnight) and then wash in warm (not hot) water with your regular detergent. If the stain still remains, repeat before drying the garment.
Those unsightly rings around your collars do come from sweat, yes, but they're also due to a build-up of dead skin and maybe some hair product too. So you can prevent much of that grit by giving the back of your neck a rigorous scrubbing during your morning shower. But for those already set-in stains, soaking your shirts in warm water and OxiClean for an hour before washing will eliminate most (if not all) of the grime. If you don't have the time or space to soak, a stain-remover bar comes in clutch. The Laundress makes a powerful one that dissolves caked-on stains.
You might've heard about the trick of cleaning your ball cap in the dishwasher. But cleaning expert and author Jolie Kerr doesn't recommend it. While that's a viable hands-off option, the extreme heat can shrink and warp your hat, plus the detergents can lead to color loss. A better option is to pre-treat stains with an enzymatic spray like Zout and submerge your hat in a sink full of warm water (with just a splash of laundry detergent). Leave it in there for a couple of hours, drain the now murky water and rinse the suds from your cap. Reshape and let air dry.