Actually, I might be talking cr*p, cos I think parafin *is* the non-carcinogenic fuel (as opposed to the usual petroleum distillates) but unless you can get the really pure stuff (which I have a hunch is what u get from those circus shops) then it might contain other additives that are harmful... cos of course filling your mouth with a flammable substance isn't harmful at all, is it?
I also remember using something called PyroFuel or PyroFluid for stage effects, which might be a similar substance.