One of my struggles as I worked towards wellness was that I continually 'Herxed', but actually I was really just very toxic and overloading my excretion systems. After 3 years of trial and error and much suffering I have found the key to this toxicity. Apparently I am a genetically super sluggish detoxer - not a good place to be. Everything that makes you better makes you worse. I found this presentation by Dr Chris Shade, a mercury detox specialist, who maps out the whole detox system so that you can get each part working in sequence so that you don't re-tox yourself and do more damage.
He also has other presentations on detoxing from heavy metals much kinder and safer than EDTA and DMSA using a Quicksilver product called IMD.