Burning Blood

You taint a living creature’s blood with a hot, corrosive infusion, dealing 1d8 points of fire and 1d8 points of acid damage at the start of each of its turns. The target creature can attempt a constitution saving throw at the end of each of its turns to negate this damage, but one successful save does not end this spell. One the creature has succeeded on three constitution saving throws the spell ends. 

Burning blood does not affect creatures without blood, such as constructs or undead.