Robbing Peter to pay Paul?

It baffles me how the body would permit candida to come to its aid? How does assembling Candida colonies in the body's battle against mercury (and other metals) ultimately contribute to health? At the same time candida may absorb mercury, it is also emitting its toxins, devouring essential nutrients, and consuming its host. It seems a sort of round-robin, but the host body is the loser.