warts are caused by virus, and anything that "kicks off" your immuno system will effect them..
the latest cure is wrapping them in duct tape (thank the ozzies for that one)

many toads (and some frogs) excrete toxins through there skin... and that some of these toxins have an effect is not surprizing. most of the toxins need to be ingested to cause damage-- since the reason for the toxins is to teach animals higher up on the food chain that it is not a good idea to even try to eat them. but some toxins do pass through the shin, (so when a bird grabs with their feet, or even a racoon with paws) the toxin will go to work immediately, before the animal has a chance to chomp down.

there is a drug, (first found by south american indians, from a mucus covered a type of frog.. ) that is a powerful, fast acting toxin that causes paralysis. frogs are pretty good eating from lots of other animals.. they have evolved a host of poisons to discourage consumption.