In theory, he had acidic sweat, but his intro was *sitting in a hot tub* with some human fans and using his power to generate an explosive blast and blow the roof off. If his power was *actually* somehow involving sweat turning to acid, he would have killed the ladies he was with rather gruesomely. Like many of the characters created during that run, the text explanations and what was actually happening on the panel often seemed to be completely unrelated, as if the artist and writer were not only in different rooms, or on different coasts, but also had never actually spoken to each other.
Still, acid sweat, acid vomit, etc. still seems more palatable than 'Clive Barker's X-Men,' the kids from Generation X, who had a dude with too much skin (Skin), a girl who rips her skin off (Husk), another dude who blew half of his face and chest off (Chamber) and another girl with no skin at all and diamond hard flesh (Penance). Yeesh. Shoulda added Marrow, for some 'ripping my bones out and stabbing people with them' action, or Maggott for 'my two stomachs burrow forth and go eat stuff' powers, just to gross it up a little more. That would give us bones, vomit, skin, stomachs, etc. Just need a mutant with powers related to blood or poop now.