The Rhus Tox I take is 6X. I take it if I have been exposed like walking in it or the dog sits on my foot and the oil gets on me. I read somewhere this year though that people who are more acidic are more susceptible and I have been more alkaline this year and even though I have been exposed, so far no poison ivy. I do take the Rhus Tox as a preventative measure since Poison Ivy is really nooooooo fun!