Go ahead and zap. I avoid the area of my body containing metal. We can zap feet, ankles, etc.
{I must avoid my right arm because I have a metal implant in the ulna bone.}

I have a friend who zaps her face because it eliminates pain from one 'loose capped tooth'. She describes a "boiling and metal taste" when she zaps in this manner. She will not allow her self to be convinced that she is releasing heavy metals into her tissues -- she is intested only in killing the pathogens which are causing the pain.

I have read that sometimes the dieing off parasites can cause that metallic taste. But just in case I would also recommend that you take some supplements to remove the heavy metal toxins from your body. It certainly couldn't hurt and might prevent a build up of things that can cause long term health problems.

Take care,
Lisa