Like was said above - poison is INGESTED (poison dart frogs secrete a poison on their skin so that when predators ingest them, they get sick, and will avoid them in the future) and venom is INJECTED.

What's interesting about poison dart frogs is that their poison is from their diet in their natural habitat. Those kept in captivity fed on fruit flies are not poisonous.

So, there are no poisonous snakes, but there are venomous snakes.