Grab some hydrogen peroxide, says author and a green cleaning expert Leslie Reichert. “If there’s a lot of blood, scrape off anything dried and crusty, then pour peroxide on what’s left,” she says. Toss the clothing in the washer and clean it as usual. If a dark mark remains, Reichert recommends using more hydrogen peroxide with a drop of dish soap. “Work them into the clothing with a stiff brush and launder again,” she says.