Poison
Definition
Paracelsus framed the working definition in 1538 as 'sola dosis facit venenum', the dose alone makes the poison. Any substance, including water and oxygen, can produce a toxic effect at a sufficiently high exposure; conversely, classical poisons like arsenic are safely measurable at trace levels in seafood. A forensic finding therefore turns on concentration and matrix, not on the substance alone.
- Foundational principle
- The dose alone makes the poison (sola dosis facit venenum), established by Paracelsus in 1538
- Forensic definition
- Any substance that produces injury, disease, or death when introduced into or absorbed by a living organism in sufficient dose through chemical action
- Key variables
- Concentration, matrix (where it is found), and route of exposure, not the substance itself
Common questions
What makes something a poison?+
A poison is any substance that causes injury, disease, or death when introduced into a living organism in sufficient dose. The key word is dose. Even water or oxygen can become poisonous at high enough exposure, while classically dangerous substances like arsenic exist safely in seafood at trace levels. The substance alone does not determine toxicity, concentration does.
Is arsenic always poisonous?+
No. Arsenic is measurable in many foods like seafood at trace levels without causing harm. The dose and route of exposure determine the effect, not the substance itself. A small amount of arsenic in food presents no injury, while a large dose absorbed through ingestion or another route causes severe poisoning.
Who first defined the dose-toxicity relationship?+
Paracelsus established the foundational principle in 1538 with the statement sola dosis facit venenum, meaning the dose alone makes the poison. This framing emphasizes that any substance can be toxic at high enough concentration, and conversely, any substance can be safe at low concentration.
Related terms
- Antemortem vs Postmortem Sample
- Antemortem samples are drawn from a living patient (most often blood, urine and gastric lavage at hospital admission); postmortem samples are collected...
- Asphyxiant
- A poison that interferes with oxygen delivery or use. Simple asphyxiants (CO2, methane) displace oxygen; chemical asphyxiants (CO, HCN, H2S) block haemoglobin...
- BSA Section 63 Certification
- The provision under the Bharatiya Sakshya Adhiniyam 2023 that governs admission of expert opinion. A forensic toxicology report carries the signature of...
- Corrosive
- A poison that destroys tissue at the point of contact by acid, alkali or oxidising action. Concentrated H2SO4, HCl, HNO3 and NaOH...
- Forensic Toxicology
- The branch of toxicology that applies analytical chemistry, pharmacology and pathology to medico-legal questions, principally the detection, identification and quantitation of poisons,...
- Irritant
- A poison that inflames mucous membranes and gut lining without dissolving them outright. Includes inorganic irritants (arsenic, antimony, copper sulphate, phosphorus) and...
- Manner of Poisoning
- The medico-legal label for how the poison reached the victim: accidental, suicidal or homicidal. Decided by the IO and the magistrate, not...
- Neurotoxic
- A poison whose primary target is nervous tissue. Subdivided by site of action into cerebral (alcohol, opioids), spinal (strychnine, gelsemium) and peripheral...
- Presumptive vs Confirmatory Test
- A presumptive test (Reinsch for heavy metals, Marquis for opioids, Trinder for salicylates) is fast, cheap and class-specific, used to triage caseloads....
- Viscera
- The standard set of organs and fluids collected at a suspected poisoning autopsy in India: stomach with contents, a length of upper...
Explained in these topics
- Classification of Poisons by Origin, Action and Chemical NatureAny substance that, when introduced into or absorbed by a living organism in a sufficient dose, produces injury, disease or death through chemical action. The...
- Introduction and Scope of Forensic ToxicologyParacelsus framed the working definition in 1538 as 'sola dosis facit venenum', the dose alone makes the poison. Any substance, including water and oxygen, can...