Pour 1/4 cup of thick corn syrup, like Karo syrup, into the mixing bowl.
Add 100 drops of red food coloring. The reason you use so much red food coloring is because the syrup is so thick that it does not disperse the food coloring well.
Drop 2 to 4 drops of blue food coloring into the mix. If it turns a burgundy or blueberry, you have to start over. It must be a dark red.
Mix in 1/2 teaspoon of flour. As you mix in the flour, the blood looses its transparency and gums up. Add more syrup and food coloring if it becomes too gummy. The correct consistency should be syrupy and not transparent.
Rub the edible fake blood over your teeth and pour it into your bottom lip to create a bloody-mouth effect.