I don't know. My Kid#3 developed nausea and headache on his antibiotic. One could easily consider it a herx/die-off. But I felt it was a reaction to the medication and for being on it so long. I decided to go off the antibiotic, and his symptoms went away and didn't return.
My point is -- when we are on these medications for longer than most use them, I think it's hard to know the difference between a herx, change in symptoms, and reaction to medication/herbals. So tough.
FWIW - headache and dizziness are listed as less serious side effects with diflucan.www.rxlist.com/diflucan-side-effects-drug-center.htm