Potion Resistance in a Pumpkin or Enchantment?

If you think about it, a lot of hazardous chemicals require inhalation to be fatal, so what if Pumpkins acted as a sort of respirator?

Example: Harming potion would do nothing, however a harming 2 potion may do like 50% decreased damage?

Or maybe there could be a helmet enchantment called "Spell Tolerance I - IV" or something like that.