I think you had what is called die-off from killing so many pathogens all at once. I have had it too a couple of times, dark pee, feeling crappy, headache for a day, but then all clear after that. Zappers put out microcurrent and I beleive it is beneficial rather than harmful as the body is bio-electric. The little bit of extra juice you get from the zapper kills the bad guys and helps your body to heal faster. My2c