Even the most hopelessly sickly of poisons can be transformed into life saving medicine. Sometimes even in small doses, they can heal wounds born of less potent toxins.
Everyone likes a little poison now and then. Otherwise, when a truly insipid strain comes along, we won't know how to react! A kid in a bubble can't survive in this world. Hell, the only difference between a little bit of poison and a little bit of candy is taste!
A poison is only lethal to the untrained being, even the poison itself.