A poison is any substance that causes harm to a living being. This can result from contact with the body e.g. a caustic or following absorption into the body. Absorption can occur following ingestion, by passage through the skin or mucous membranes, by inhalation or by injection. The foetus can also be poisoned by a substance crossing the placenta. Almost any substance can act as a poison if a sufficiently large dose is absorbed.

The National Poisons Information Centre established in the Department of Pharmacology at the All India Institute of Medical Sciences (AIIMS), New Delhi, provides information round-the-clock on various poisonings and treatment protocols on telephone, fax and e-mail.