"Why is there blood here?"
Translation:Почему здесь кровь?
Based on comments elsewhere, the presence of есть in a question signifies questioning whether something exists or not. (есть is not "to be" but more "to exist"). There's no question the blood exists, the question is about why it's present. So, есть is not applicable here.
How about "У вас есть кровь?", are questions about possession special? I was thinking of leaving есть out in the question, but put it in because it's more likely that someone will be shocked about the fact that there's BLOOD, instead of why there's blood again, but in that specific PLACE.