User blog comment:Ultraprime2/Fairy Tail Wikia Podcast 29/8/2014/@comment-24744901-20140830150225/@comment-24800928-20140830182917

the poison is just carbon which is non-toxic (it would only be poisonous from over-consumption), so the body should adjust soon. Also Levi could possibly easily cure all of them. especially Natsu by just some fire.