Best stain remover for blood?

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DD has just started her periods and has had a few leaks. I'm soaking in cold water but could do with some sort of stain remover - any recommendations?

Cold water and dishwashing liquid works wonders, also on grass and mud

I do a 30 degree long wash with biological liquid and also add vanish (or similar) if I have it. Works well. I got the 30degree tip from Nancy Birtwhistle, as I would have thought 30 degrees is too hot for blood.