"Blood is really difficult to remove," Weiss says. Still, it's doable, and the sooner you get to it, the better your odds. Generally you want to use cold water to remove protein stains like blood (or any other bodily fluids for that matter), because hot water can set in the stains. Ideally, don't let it dry, and wet it from the back side of the stain, "otherwise, you're forcing it deeper into the fabric," Weiss says. Keep rinsing until the water comes through clear. If that doesn't get it completely clean, then try hydrogen peroxide, which works well; however, as with any product, be sure to try it first on an inconspicuous part of the fabric to test whether it causes discoloration. When the hydrogen peroxide stops bubbling, rinse the fabric in cold water; rinse and repeat if necessary.