Free your favorite white tees from unsightly yellow stains this summer (and all year!).

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You know it's time to take action when your white shirts start coming out of the wash still sporting underarm sweat stains. But don't worry, it's not you—it's science. Really! Dark or yellow sweat stains are most often caused by a combination of the salt in your perspiration, what you eat, and the type of deodorant you use. Wondering if anything can be done to remove sweat stains from your clothes? Before calling it quits and tossing out a stained shirt, give these tips a try.

Take Precautions to Prevent Stains

The first thing you can try to do is prevent these kinds of underarm marks from forming in the first place. Don't dress immediately after applying deodorant—wait a few minutes for it to dry. In a rush? Pump a few shots of air from your hair dryer under your arm, then get dressed. Letting your deodorant dry first will help prevent the depositing of deodorant and moisture into the underarm of your white shirt. Then, if you're out and start to sweat, sneak to the restroom, take a paper towel, and dab your underarm area. If you discover the underarm of your shirt is wet, don't give up.

Remove Sweat Stains ASAP

The last thing you want to do is let a shirt with sweat stains sit around for a few days without attempting to clean it, says clothing expert Steve Boorstein (aka The Clothing Doctor). Yellow stains tend to take hold over time, not as a result of wearing the shirt once. Use a product, such as OxiClean (according to the manufacturer's instructions), immediately. Or create a solution of one part water to four parts dish washing detergent. Place the solution in a spray bottle and lightly spritz just the underarm area of the washable T-shirt. Use a toothbrush to rub the area gently to break up the stain. Let it sit for a few minutes. Then launder it according to the label instructions.

For non-washable white tops, try blotting the underarm area with a small amount of water. (You don't want to use too much water, which it could leave a ring.) A last, but very helpful, resort? Take your top to the dry cleaner.