Mix red food colouring with water, add half a tea spoon of cornflour to add thickness to the mixture

Awesome, thank you so much!

:)

For me, I usually use glue and red food dye, but depending on how thick you need it, you can add water. :3

I've used water or baby oil mixed with red food dye and a little bit of cocoa powder. Works great. But it will wreck any clothes it touches

Thanks guys! I will try them out!

Maybe you have to add a little (!) bit of blue dye, because blood isn't 'pure' red, it's a little bit darker