Re: the zapper can definitely be felt at much lower frequencies.

Thanks, parazapper, Which explains why I've never felt my Clark zapper. I felt faint buzzing tingling from the fungus frequencies zapper though, is that why?

And I must confess, it seems unlikely to me that killing parasites could be accomplished by a placebo effect. You got to apply current of one sort or another.

Dr. Clark chose 30 kHz because she felt it was about the most optimal level, but noted that any frequency would work probably down to 5 kGz. I'm guessing she might have gone with 30 hKz partly for the lack of sensation. To avoid frightening the average new user, although she never actually said so.