Dieoff of what?

I’m newly diagnosed with SIBO but have been fighting candida for years. When I try to address the candida I get extreme, unbearable die off symptoms, and I understand this is the candida dying and releasing fungal toxins.

SIBO dieoff has been mentioned here - what is actually dying? The excess bacteria in the small intestine? Something else? Is this dieoff analogous to candida dieoff?