User blog comment:Roy1313/Dimaria's Power/@comment-25111584-20160211163014/@comment-2214433-20160212204352

Gray's power could've also acted up = unintentionally killing Frosch

Possibilities are endless... But the fact that Igneel and others worked for years in order to make sure that Natsu and co. don't turn into dragons, not even coming out when Acnologia attacked for the first time because their literal priority was to make sure they don't create 5 another Acnologia-like dragons, and the fact that Gray went to Porly for remedy (I mean... turning into a demon sounds bad enough, but there clearly were other effects) just speaks for the statement of both dragonification and demonification not being the best things out there.