Neither frogs nor toads cause warts, a human virus causes warts.
Toads secrete a slimy substance out of glands in the back of the head that can cause an allergic reaction in some people.
Its primary function is to make a toad taste horrible to anything looking for amphibious cuisine.
The bumps on a toad’s skin are not warts but help the animal blend into its environment visually by breaking up its outline.
Think of it as commando amphibian camouflage.