Mind of tempest
(he/him)advocate for 5e psionics
I assume it is more their environment has plenty of toxic elements in it thus they developed a very efficient system to deal with the natural hazards.I like to think the Dwarves developed a resistance to poisons because of their love for forging. Think about it, in RL the forging of metals creates poisonous by-products. While there are ways in RL to protect yourself from these poisonous by-products, the Dwarves in a fantasy setting don't really have them. They had to build up a resistance to them over the course of several Dwarven generations. And it's a possibility that this resistance eventually spread to other kinds of poisons.
also dwarven strong drinks should be utterly toxic to humans, pure ethanol level toxic