Don't Lick the Toads

In the practice of handling amphibians, it's worth noting that you need to keep hands clean not just for the safety of the animal, but for you as well.  Granted, you should wash your hands after touching any animal, but with amphibians there is a special imperative.  Many species secrete toxins through their skins - the poison dart frogs are the most famous examples, but so do a wide variety of other species.  

Again, these secretions are poisonous, which means they are absorbed - assuming it doesn't bite you, you could pet a king cobra or other venomous snake all day with no ill effect, as those toxins need to be injected.

It's the absorbent nature of amphibian venom which has, among other things, given rise to the trend to licking certain species of toad to get high off of their toxins.

These poisons aren't just a potential safety concern for keepers and predators.  They can also pose a threat to exhibit-mates.  Some amphibians can be a challenge to house in mixed-species exhibits, as they may, say, soak in a water bowl and secrete their poison, to the deleterious effect of other species in their enclosure.