If you get dizzy or heavy headed, then exit and take a looooooong brake or give it a quit for the day and enjoy the results for a couple of days before the redistribution kicks in.. Its not recomended to push it..... it can be potentially dangerous.... With me it feels like a metalball in my head.... that is when i quit a session... You can say i sometimes push it to the edge, but then again its when i do that i get the best results!
The heavy head will go away after half an hour or so when finished... sometimes hours... depends on the day... no day is the same...
Drink plenty of water inbetween sauna re-entries too... every 5 visits maybe...
Just remeber to have a good mineral base when doing this!

Sauna is a good alternative to DMSA i think... i'm not touching that stuff yet...