I`v been using a cheap clark zapper from ebay. I have candida, leaky gut and prostatitis diagnosed from a reputable ND.
The prostate issues diminished considerably after three days of using the zapper.
As far as the candida and leaky gut are concerned, the zapper has failed to alleviate those problems. Even after two weeks of religious zapping they seem untouched.
Also some good info concerning the recent flu bug my whole family has received. We all have used the zapper for the past week and there has been absolutely no improvement with any of us. I even stepped up the voltage input from 9 volts to 12 for a few days using on myself with no improvement.
I believe from personal experience the zapper can help a little with certain health problems but it is in no way a cure on its own.