All potatoes naturally contain solanine, which is poisonous in large quantities  Domesticated potatoes contain only very small amounts of solanine, but many wild potatoes contain poisonous levels of solanine
Since most of the solanine in potatoes is concentrated in the skin, however, peeling wild potatoes makes them at least as safe to eat as unpeeled domesticated potatoes of the same size
The amount of solanine concentrated in the skin of a wild potato is large enough by itself to be poisonous.