Flesh Allergy

If Flesh Allergy resolves but the targeted creature is not destroyed (because it has indestructible or enchanted by an Aura with umbra armor, for example), its controller will still lose life.

You must sacrifice exactly one creature to cast this spell; you cannot cast it without sacrificing a creature, and you cannot sacrifice additional creatures.

Players can only respond once this spell has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.