Well, according to an old post by fastician/Milena, a headache could be detox-related: //www.curezone.org/forums/fm.asp?i=1818109#i
- but I don't really know anything about that. I've not experienced a headache on any waterfast or dryfast yet (and the longest ones have been 6 days and 2 days, respectively). May attempt a 3-day-long dryfast very soon.