Peroxide can remove blood from many things. Test a small area to make sure that it will not bleach the surface to which it is being applied.
If the stain is fresh, rinse it in cold water. Apply hydrogen peroxide to the area and wash as normal. If the blood has dried, rinse it and brush it off to remove the top layer. For blood stains on carpet, mix dish detergent with cold water and blot the area with a white cloth. This step may need to be repeated a few times. If the stain is persistent, mix ammonia with water and apply to the dirty area.