The only way one can become immune to a poison is if he/she takes very small doses (amount depending upon the poisons toxicity) and increase this amount slowly until ones system becomes familiar with the poison. This can change depending on the poison, as there are some varieties that you can not build up any sort of immunity to.
No.
Immune
So then it doesn't have full effect on your body however just enough for your body to be immune.
Yes the only animals to be allergic to poison ivy are humans.
Yes it will.
There is a species of snake that is immune to them.
Poison Ivy is not REAL Poison. Its a issue in the immune system that will make it react to you. If you have a serious case or allergic reactions you would need to seek medical attention.
Alligators aren't immune to snake poison, Rat poison is questionable. I imagine it'd have to be a hefty dose to take out an adult alligator though.
Yes but only if you take a very very vary small doses. But like a dog with chocolate, to much will kill.
You can.
No.Different creatures are more (or less) resistant to certain toxins and poisons. All creatures can be poisoned. You have to choose the right poison.
Probably a snake that is more or less immune to the poison, as with the Golden Dart Frog, which can be eaten by a snake: Leimadophis epinephelus.