How do I keep white knits white?
First, determine whether the stain is oil- or water-based. Water-based stains include most beverages, like juice and wine. These may seemingly disappear into your clothing, but a water-based stain will usually leave a slight ring around the stain as it absorbs into the fabric. Oil-based stains come from items like salad dressing and perfume and are more evenly absorbed into the fabric.
Water-based stains should be washed within one to two days of the spill. If you don’t notice it until the stain has turned yellow, Steve Boorstein, founder of Clothingdoctor.com, recommends soaking the garment in four inches of warm water mixed with either OxiClean Versatile ($10, greatcleaners.com) or a color-safe bleach for about 30 minutes, or until the stain disappears. For more options, see our round-up of the best laundry detergents.
Oil-based stains are trickier to remove, so leave them to a professional. The sooner you take in the clothing, the better. And be sure to confirm that the dry cleaner can remove oxidized oil stains (a process not all cleaners perform). ―Melanie Wagner