The principles of toxicology existed over 500 years ago, joining multiple disciplines of knowledge, such as pharmacology, medicine, and chemistry. Fundamental aspects of toxicology was brought about by Paracelsus, a sixteenth-century physician, who denoted that the dose of the chemical or poison is what makes the poison lethal. This ideology introduces the importance of the dose-response curve in the field of toxicology-that as the dose of a drug increases, its negative impact on health also increases. There are also other aspects of chemical compounds that influence the adverse effects, such as route of administration, chemical structure, and type of exposure. Toxicology’s dose-response curve represents how a population will respond to a particular dose of a specific drug or chemical.