While removing dried a bloodstain is tougher than removing a fresh stain, the best methods involve removing as much of the surface stain as possible and then soaking the garment in cold water. After the stain is wet again, options for removal include using hydrogen peroxide, lemon juice or ammonia.
Hydrogen peroxide is a mild oxygen bleach that is often effective on blood. It usually does not affect colors, but the user should test it in an inconspicuous spot before using it on blood. However, chlorine bleach reacts with blood to cause permanent stains.
Lemon juice, which is acidic, helps to remove bloodstains. Juice from a bottle or squeezed fresh from a lemon are works. Allowing the juice to sit in sunlight helps to reduce the bloodstain, but is likely to bleach dark colors.
Ammonia is another option. Household ammonia has a strong smell and should be used in a ventilated area.
Stain removal should always begin as soon as possible after spilling blood on the clothes. Stains that are over 24 hours old become almost impossible to remove. When the stain occurs away from home, treating it with cola or another flavor of soda can help to prevent it from becoming permanent. At home, the garment should soak overnight in more cola before laundering as usual.