Toxicology is that branch of Science which deals with the study of various poisons, their effect produced on a living body, their detection and isolation. The study also includes the range of toxicity, toxin principle involved, the mechanism, the ante-mortem signs and symptoms, the post-mortem appearances and the medico-legal significance's of the various poisons.

Mathieu Orfila, a Spanish-born French Toxicologist and Chemist, is considered the Father of Toxicology. He is known for creating new techniques and refining the existing ones in order to enhance and achieve better accuracy in the determination of poisons. In Orfila's time, the primary type of poison used was Arsenic. According to Paracelsus, a Swiss-German Physician, €Everything is a poison, there is poison in everything, only dose makes a thing not a poison.€
In the present epoch, the poisons have been classified into various categories depending upon the state of matter they belong to the body organ they target on the origin they belong to other such factors. Broadly speaking, the poisons can be classified as: Volatile poisons, Metallic poisons, Corrosive poisons, Insecticides, Pesticides, Barbiturates, Plants poisons, Animal Poisons and so on. The toxicity and the effect produced by a certain poison basically depend upon the dosage or the range of exposure which can be acute or chronic.

The common poisons used for recreational purposes are: Alcohol, Caffeine, Cocaine, Opium (including heroin and such other substitutes), Cannabis, Dhatura and many more. Among all, alcohol is the most common. These types of drugs are categorized as Drugs of Abuse and are known to induce euphoric feeling instantly, but later on leads to the depression of Central Nervous System. Certain drug as opium is also taken to aid masculinity, strengthen sperm and regain vigor in order to fulfill one's sexual gratification. Accidental deaths have been recorded by various plant poisons as Calotropis, Ricinus, Nerium and so on. The post-mortem appearances are of significant value in the study of toxicology as they are of much importance in determining the poison that contributed in the crime and finally led to death. The other parameters to be considered in the detection and the isolation of any poison are the examination and a thorough analysis of the visceral organs, stomach wash and vomit specimens, if any.

Even the primordial pages of history clasp infinite incidents of poisoning. Socrates, the classical Greek Philosopher was sentenced to kill himself by drinking poison hemlock. Even the most beautiful and spectacular Egyptian Pharaoh Cleopatra is known to murder herself by being bitten by a cobra on her breast. Recent studies have even revealed that, the famous French Military and Political Leader Napoleon Bonaparte was also killed by chronic Arsenic Poisoning, traces of Arsenic have been found in the preserved hair samples of the deceased.