Toxicology is the study of poisons, or toxins, and how they affect living organisms. It also includes investigations of toxins in the environment, how they are distributed, and the risks they present to plants, animals, and people. Toxicology draws on several areas of science including biology, chemistry, mathematics, and physics.

Human awareness of poisons predates recorded history. The earliest humans used toxic plant and animal extracts for both hunting and warfare. In ancient times and during the Middle Ages, knowledge of toxins was well-developed. However, a parallel gain in knowledge also took place with regard to medicines. In the late Middle Ages, Paracelsus (1493-1541), a physician-alchemist wrote: "All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy." At the time, his views were seen as revolutionary, but they mark the beginnings of modern toxicology.

By the late...