Ideally, you'll tackle blood stains while they're still wet, which makes them easier to get out. But they're definitely a challenge. This video shows the best way to treat them.
Bowl or sink filled with cold water, bar of soap, stain-removal spray, ammonia, cotton swab, paper towel, laundry detergent
If the stain is fresh and still wet, soak fabric in cold water immediately.
Rub the stain well with a bar of soap, lathering gently.
Tip: For light-colored fabrics, dab with a hydrogen peroxide, which acts as bleach.
If the stain has already dried, spray with stain-removal solution. Let it soak in.
Apply a small amount of diluted ammonia to the area with a cotton swab.
Machine-wash the fabric using an enzyme detergent (most standard laundry soaps are enzyme-based), which breaks down protein stains. Make sure the blood has lifted before putting fabric in the dryer, as the heat will set the stain.