>- I have have fine vertical lines on the skin on my fingertips
I have never heard of a zapper causing something like this. I would certainly check for any deficiency such as calcium, magnesium, etc. I have been zapping for 6 years and have never seen any such problem with my hands.
Also, how are you zapping? How much are you zapping? What zapper are you using? Do you alternate the electrodes from one hand to another? What electrodes are you using? Are they copper or something else like stainless steel? Do you use salt water or drinking water on the paper towels or napkins over the electrodes? Have you changed any of your foods or drinks recently?