Poisoning occurs when a toxic substance is swallowed, inhaled, or absorbed after coming in contact with the skin, eyes, or mucous membranes. Poisoning is also called toxicosis or intoxication. Because pets are unable to tell whether a substance is poisonous or not, they are often poisoned by eating something toxic, such as antifreeze or a poisonous plant. Pets can also be poisoned by a sting or bite from a venomous insect or snake, or even by a well-intentioned owner giving human drugs that are poisonous to animals.

An animal can be poisoned after a single exposure (with effects most pronounced during the first 24 hours) or after repeated or prolonged exposure to a poison. All toxic effects depend on the dose—the amount of poison present—and on the species. A small dose may be undetectable and have no harmful effects, while a large dose can be fatal.

Last full review/revision July 2011 by Barry R. Blakley, DVM, PhD; Cheryl L. Waldner, DVM, PhD; Rob Bildfell, DVM, MSc, DACVP; William D. Black, MSc, DVM, PhD; Herman J. Boermans, DVM, MSc, PhD; Cecil F. Brownie, DVM, PhD, DABVT, DABT, DABFE, DABFM, FACFEI; Raymond Cahill-Morasco, MS, DVM; Keith A. Clark, DVM, PhD; Gregory F. Grauer, DVM, MS, DACVIM; Sharon M. Gwaltney-Brant, DVM, PhD, DABVT, DABT; Larry G. Hansen, PhD; Safdar A. Khan, DVM, MS, PhD, DABVT; Garrick C. M. Latch, MASc, PhD; Gavin L. Meerdink, DVM, DABVT; Lisa A. Murphy, VMD; Frederick W. Oehme, DVM, PhD; Gary D. Osweiler, DVM, MS, PhD, DABVT; Mary M. Schell, DVM; David G. Schmitz, DVM, MS, DACVIM; Norman R. Schneider, DVM, MSc, DABVT