Why is my zapper burning me now?

Hi to all!! I'm hoping someone out there can help answer this question for me. I started using a Terminator II zapper about 6 weeks ago. When I first started using it, I was getting some stinging sensations that I considered normal reactions (build up of acids). The sensations went away after a while. However, this weekend, after changing the battery, my zapper is burning me like crazy. I can only wear it for 5 minutes and I get burn marks. And one of the pennies turned very black.
Does anyone know why this would happen? Did I break it somehow? I had a friend try it and it burned him too. I've been doing some bowel and parasite cleansing, so could it be that I've stirred up a whole bunch of stuff??
Any and all thoughts are very much appreciated!!
THANKS Tweet