I took blood root salve (which had zinc chloride) internally without adverse reaction. I would take it for about 3 weeks at a time, stop for a couple weeks, then do another round. Actually, it helped decrease a persistant fullness in my stomach. I'm pretty sure it was parasite related.
Not to say you should take it internally, and especially if you have reservations about it....just thought I'd share my experience with it...it was a good experience.