User blog comment:IamJakuhoRaikoben/Chapter 480: The Northern Gravestone, Review./@comment-24792841-20160405070825/@comment-7418318-20160405124920

Gajeel also has blood coursing through his veins. He just turns his skin into metal, so he wouldn't be immune to blood-manipulation, unless that magic can only penetrate skin and clothes, but not metal, which is highly unlikely.