Paracelsus’s rule still runs modern poison science
Toxicology studies how chemicals harm living things and how to diagnose and treat exposures. Dose, duration, route, species, age, sex, and environment all shape risk. Paracelsus’s sixteenth-century line—“the dose makes the poison”—still anchors regulators from the FDA to the WHO.
The English word toxicology appears around 1799 from Greek roots for poisonous and subject matter. Older practice runs deeper: Egyptian records mention antimony, arsenic, lead, opium, and mandrake, and careful notes on snakes and scorpions; tradition credits the early pharaoh Menes with studying plant poisons and venoms. India's Kalpasthāna section of the Suśrutasaṃhitā, composed before about 300 CE with parts possibly from the fourth century BCE, classified plant and animal poisons and later influenced Arabic and European medicine. Dioscorides tried to sort plants by toxic and therapeutic effects in Nero's court; Maimonides wrote a twelfth-century book on poisons and deadly drugs.
Paracelsus is often called the father of modern toxicology for insisting that only the dose decides whether a substance is a poison. Mathieu Orfila gave the subject its first formal treatise in 1813. In 1850 Jean Stas isolated plant alkaloid poison from human tissue, proving nicotine in the Bocarmé murder case. Today agencies such as the FDA, EPA, and WHO run standardized risk assessments; the FDA Redbook 2000 guides food-additive toxicology. Assessment asks which adverse effects appear by oral, inhalation, or dermal routes and at which acute or chronic doses, including cancer studies.
Classic metrics include LD50 (dose killing half an exposed population), NOEL, NOAEL, and OSHA's PEL. Most chemicals show a threshold below which nothing is seen; a few lack a clear safe level or bioaccumulate and get special scrutiny. Since the late 1950s the Three Rs have pushed reduce, refine, and replace animal tests; the EU banned cosmetic animal testing in 2013. Model organisms range from zebrafish and C. elegans to Galleria mellonella. In 2007 the U.S. National Academy of Sciences urged a pivot to human-cell and computational methods; EPA's ToxCast work on 1,065 substances predicted developmental toxicity for 19% with roughly 79–82% accuracy versus animal prenatal models.
Source: Toxicology
