Is it true that one can take low concentrations of poisons over a period of time?

Question

...and build an eventual resistance to the poisons full concentration?

Answer 1

Smokers do it all the time, but they don't build up a resistance to any of the thousands of poisons they ingest.  Instead, the cumulative effects cause irreversible damage to almost every organ system.

Answer 2

it depends on the poison and the way it affects your body. some allergens actually cause a more significant reaction if you are exposed to them more than once to others you may develop resistance or tolerance and some will kill you dead at very low doses.

Answer 3

It's an ancient literary device, but depending on the substance, the reverse is more likely in the real world.