"Poison is in everything and no thing is without poison. It is the dosage that makes it either a poison or a remedy."2
1See Paracelsus; A 16th century Swiss physician who described the role of herbs in medicine as such.
2Merry S. Baum, Herbs: The Roots of Medicine, HealthState, 21st Century Medicines, Volume 9:1, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, Winter/Spring 2001.