User blog comment:Goregutz619/HXH episode 138 discussion/@comment-14902757-20140720215848/@comment-24287488-20140721053204

Most probably someone must've tried to heal him before, that's why...

Gon did put a restriction on himself for exchange of that super powers at the cost of his life. So naturally what he did was odd... no one has seen any case, something like this before...